Tuesday, May 21, 2013
Luck vs Skill - Are picks after trading up better than others?
As some of you have no doubt noticed I have spent my last few posts looking at the level of skill involved in the NFL draft. Whether it’s year-over-year or individual selections in the same year, I have had no luck finding an outcome in which skill appeared to play a significant role.
For my third cut at the subject I am trying a narrower focus in search of skill: draft day trades. Specifically, I will be looking at the highest pick involved in each draft day trade. These trades ought to show us the picks about which decision makers were most confident. They had to offer enough compensation to the pick’s owner to induce them to trade and they did it with a specific player in mind. Though these trades include all transactions on the day of the draft, a great majority of them were consummated during the selection window, only when that pick granted the right to a specific player the team trading up desired.
Thanks to the fantastic website www.prosportstransactions.com I was able to work quickly through the data collection phase and identify those trades that took place on draft days from 1994 to 2006, the same period as my previous post. After working through the details[1] we are ready to go.
That value chart is irrelevant because teams are trading for specific players
Long story short: there is still nothing to see here. Out of 245 picks in the data set, 108 were “good” according to the value expected by the Sports + Numbers draft value chart. Given the distribution of picks we would have expected 104. Not a good sign to start.
The individual p-values are nothing remarkable and those of rounds 3 through 5, flirting with a whole 50% chance of non-random difference from average, could be substantially undone by a single additional bad pick, their values retreating to 83%, 79% and 77%, respectively. These are not robust findings of skillful GMs swindling their dimmer peers for an overlooked gem.
One of the more common retorts of those confronted with a trade that looks unfavorable according to the draft value chart (any of the draft value charts) is that teams are trading for specific players rather than some nebulous conception of value – so the trade can’t be evaluated by those fancy charts. The results of this analysis directly contradict that interpretation of trades because the players selected after trades appear to be as successful (or unsuccessful) in the league as those selected in the normal course of the draft. Therefore, the value chart seems like a pretty good way to deal with trade evaluation.
Top picks too
A few peeks at the early first round trade up picks might help head off some of the “..but what about ____?” comments.
Cutting up expected success rates by round is somewhat arbitrary, as I noted in my earlier post, so would it make a difference if we just look at the really high picks? The overall first round expected success is 51.6% while the top 10, including both traded and non-traded picks, comes in at 50.8% even against much higher expected value (see all the details here).
The 17 top 10 picks that were traded only feature 7 (41%) that turned out to be good picks. While some of the good ones were very good (Eli Manning, Walter Jones, Champ Bailey) some of the bad ones were very bad (Ki-Jana Carter, Trev Alberts, Jonathan Sullivan).
Expanding out to the full first round for a bigger sample, the average surplus of the trade up group of is 5.08% while the non-trade up group comes in at 4.21%[2]. This difference in performance is worth just over $1 million in career salary cap value. It’s not nothing, but it’s not much spread over the average 8+ year careers of these players (some of whom are still playing). In terms of draft picks it is worth something like the 240th pick, a mid-7th rounder.
[1] I included the top pick involved in picks for picks transactions or players and picks for picks transactions, provided the side with a player on it did not have the highest pick among those transacted. I also included pre-draft trades of the number one pick – and mid-draft trades of Eli Manning – because the team selecting first gets their choice of player and I assumed that they had one in mind. The higher pick is the only one included in the data set. The evaluation of a “good” pick depends only on the production of that pick relative to the expectation and not on the players eventually selected with whatever was traded away. That is more than enough fine print for one post.
[2] The difference is positive for both because the last several years of drafts are not included, where players have had shorter careers that depress the total value in the full set. I’m working on some revisions to my value chart that will take the growth curve into account and get at a better estimate of total career value.
Labels:
Luck vs Skill,
NFL,
NFL Draft,
Trade
Friday, May 10, 2013
Luck vs Skill - Is anyone good at picking football players?
A couple of weeks ago I took a look at the randomness in NFL Draft results, prompted by articles from Brian Burke and Chase Stuart on advancednflstats.com and footballperspective.com, respectively. I found some slim evidence for skill in drafting – the streaks of drafts with outperformance were slightly longer than expected. Interestingly there was much stronger evidence that some teams are not good at drafting, but you can read that post to get the details there.
The year-over-year data, however, has a major issue that I mentioned in the post: it’s not the same people making the decisions. Looking at the picks made by the Browns in 2012 and those made in 2013 provides no insight because the regime had turned over in the interim. Above and beyond that, the competitors do not behave similarly year to year so the decisions of each team – the variable we are trying to evaluate – are mixed in with changes in the way that other teams decide.
In response to these problems it seems like a study of the picks within a single year would be the place to look. The premise is that any team that has made a good pick should be more likely to make a good pick with their selection. If the initial pick reveals anything about their skill level, the subsequent success rate will exceed that of teams with a miss on their previous selection.
Using my data set of draft performance in the salary cap era[1] and my analysis of what a draft pick is really worth, we can quickly look at which picks were successful by identifying the ones that delivered more than the expected value. The percentage of picks that are successful varies widely by round due to scouting focus and the binary outcomes in later rounds[2]. If a player makes it and stays in the league for a couple seasons, they probably generate enough value to be a success because the expected return is so low in later rounds. Most of the picks in these rounds wash out: 269 of the 569 7th round picks play 1 season or less, and a grand total of 0 of them delivered value in excess of their expectation.
Monday, April 29, 2013
2013 NFL Draft - Evaluating the Day 3 trades
Note: See Day 1 evaluation here and Day 2 here
Time to dig into the trades from Day 3 (rounds 4 through 7) of the NFL Draft. As with the previous two days, here is a graphical representation of the trades from Day 3 of the draft as calculated by the Sports + Numbers draft value chart (explained here).
1. What is Cleveland doing? – After praising the Browns yesterday for taking advantage of a team using the old chart, making the Dolphins believe they received value equal to a fifth rounder for receiver Davone Bess when the Sports + Numbers chart shows the Browns only parted with the value of a sixth round pick, these moves look questionable. These were straight-up this year for next year one round ahead picks, so why the discrepancy? In an effort to bring some standardization to the process, I calculate the discount rate on picks as an actual discount rate rather than the NFL standard of “one round per year.” The effective discount rate of NFL teams, as found by Cade Massey and Richard Thaler, is somewhere in the vicinity of 136%. If you leave everything equal and vary the discount rate, the Browns would have to be using an annual rate of 61% to make the Pittsburgh trade “fair” to both teams and 23% for the Indianapolis trade. 61% is a pretty insane discount rate (think what would be used if I wanted to do an NPV for a loan shark) while 23% is still on the high end. Given that the new front office smell is still floating around in Cleveland, the Browns brain trust may be assuming that they have the luxury of time and trading at a lower discount rate than the standard, very high, rate that the NFL uses. The other option here is that the Browns are not using any new chart at all and they simply valued Bess at a 5th round level yesterday. As for the later trade with the Colts, given that Indianapolis came up very Lucky (pun intended) and had an expected win-loss of 7-9 based on their point differential, the Browns may have tacked a few extra slots of mean reversion onto their analysis of where the pick would be in 2014. Time (and Andrew Luck) will tell if that is a wise strategy.
2. Not a lot of evidence for new chart use – These trades simply do not line up according to the Sports + Numbers chart (or any new version). While the premiums involved are small, there is scant evidence here for a change in mindset of NFL teams.

3. Thoughts on the existing chart – Looking at the trades through the Jimmy Johnson chart, it remains clear, as it has been on other days in this draft, that a lot of teams use it as both a starting point and ending point for negotiations.
Saturday, April 27, 2013
2013 NFL Draft - Evaluating the Day 2 trades
Note - See Day 1 evaluation here and Day 3 here
As with yesterday, here is a graphical representation of the trades from Day 2 of the draft as calculated by the Sports + Numbers draft value chart (explained here).
1. Smart teams trading with each other - I don't think it's a coincidence that the two trades that stand out as being very close to equal value are both between Green Bay and San Francisco. The only way that those go through is if both teams accept a different perspective on the value of picks. The slight overcompensation goes to Green Bay as the team trading down.
2. Draft picks are made out of people - Two trades involved real, actual players in combination with draft picks. Miami-Cleveland, shown at far right of the graph, shows only the picks involved in the trade. Given the 4.5% value of the gap, this puts Davone Bess's value equivalent to the 182nd pick overall, midway through the 6th round. The Jets' trade for Chris Ivory, late of the New Orleans Saints, is much easier. The 106th pick, worth 10.9% of the first overall, was traded straight-up for Ivory.
3. More evolution than revolution - As with yesterday, most of the trades conform to the existing "Jimmy Johnson" chart in use since the early 90s.
4. Cleveland pulls a fast one - According to this chart Davone Bess is valued at 1.7%, but because the values decline so much faster on this chart that would be the 142nd pick. Given Miami's conformity to the existing chart in other trades, this represents a bonus to the Browns as they gave up what they consider to be worth a 6th rounder and the Dolphins believe they picked up a 5th rounder. The 106th pick, exchanged for Chris Ivory, is worth 2.7%.
As with yesterday, here is a graphical representation of the trades from Day 2 of the draft as calculated by the Sports + Numbers draft value chart (explained here).
1. Smart teams trading with each other - I don't think it's a coincidence that the two trades that stand out as being very close to equal value are both between Green Bay and San Francisco. The only way that those go through is if both teams accept a different perspective on the value of picks. The slight overcompensation goes to Green Bay as the team trading down.
2. Draft picks are made out of people - Two trades involved real, actual players in combination with draft picks. Miami-Cleveland, shown at far right of the graph, shows only the picks involved in the trade. Given the 4.5% value of the gap, this puts Davone Bess's value equivalent to the 182nd pick overall, midway through the 6th round. The Jets' trade for Chris Ivory, late of the New Orleans Saints, is much easier. The 106th pick, worth 10.9% of the first overall, was traded straight-up for Ivory.
3. More evolution than revolution - As with yesterday, most of the trades conform to the existing "Jimmy Johnson" chart in use since the early 90s.
4. Cleveland pulls a fast one - According to this chart Davone Bess is valued at 1.7%, but because the values decline so much faster on this chart that would be the 142nd pick. Given Miami's conformity to the existing chart in other trades, this represents a bonus to the Browns as they gave up what they consider to be worth a 6th rounder and the Dolphins believe they picked up a 5th rounder. The 106th pick, exchanged for Chris Ivory, is worth 2.7%.
Friday, April 26, 2013
2013 NFL Draft - Evaluating the Day 1 trades
Note - See Day 2 evaluation here and Day 3 here
A few quick-hit thoughts on the yesterday's trades during the first round. First, here's a graphical representation of how each team did. The units, as always, are percentages of the value of the first overall pick.
1. Don't trade with the Patriots - Just don't. You won't win the trade. New England absolutely mauled the Vikings with this trade, getting a bigger haul than the Cowboys or Rams despite trading 11 and 7 picks, respectively, behind them. The excess value received by New England is roughly equal to an early 3rd round pick.
2. A new way of looking at deals - It looks like things might be moving closer to the reality of what the players are actually worth as the Oakland-Miami deal represents pretty close to fair value according to the revised chart...
3. Long live the Jimmy Johnson chart - ...but there is still a lot of inertia around the classic chart spread around the league two decades ago. Only the Oak-Mia and Dal-SFO deals varied in any meaningful way. Everyone else - I'm looking at you St. Louis, Atlanta and Minnesota - paid out way too much value because their trade partners got them to deal on terms much more favorable to the team trading down.
4. Some additional reading - Both Chase Stuart at Football Perspective and I have put out analyses of which positions are successful (and which are not) in the first round. Two excellent reads if you have some time. Brian Burke from Advanced NFL Stats also had a post this week with some thoughts on economist Cade Massey's work on the draft (some with Richard Thaler) and the implications for NFL teams. If you enjoy the type of analysis on my site, go get much better versions of it at Brian's site and the links he cites.
A few quick-hit thoughts on the yesterday's trades during the first round. First, here's a graphical representation of how each team did. The units, as always, are percentages of the value of the first overall pick.
![]() |
| 2013 first round trades in the NFL Draft according to the Sports + Numbers draft value chart |
2. A new way of looking at deals - It looks like things might be moving closer to the reality of what the players are actually worth as the Oakland-Miami deal represents pretty close to fair value according to the revised chart...
![]() |
| 2013 first round trades in the NFL Draft according to the existing "Jimmy Johnson" draft value chart |
3. Long live the Jimmy Johnson chart - ...but there is still a lot of inertia around the classic chart spread around the league two decades ago. Only the Oak-Mia and Dal-SFO deals varied in any meaningful way. Everyone else - I'm looking at you St. Louis, Atlanta and Minnesota - paid out way too much value because their trade partners got them to deal on terms much more favorable to the team trading down.
4. Some additional reading - Both Chase Stuart at Football Perspective and I have put out analyses of which positions are successful (and which are not) in the first round. Two excellent reads if you have some time. Brian Burke from Advanced NFL Stats also had a post this week with some thoughts on economist Cade Massey's work on the draft (some with Richard Thaler) and the implications for NFL teams. If you enjoy the type of analysis on my site, go get much better versions of it at Brian's site and the links he cites.
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