In a previous post I discussed how INTs and INT return yardage influenced starting field position (SFP). I will extend that discussion to include each of the other events that directly result in SFP: turnover-fumble returns, kick and punt returns, and missed field goals by opponents. As an aspiring defensive back, I of course took great care discussing interceptions. I will devote little discussion here to fumble recoveries and missed field goals. I will harp on kick-off returns but refrain from discussing punt returns at any depth.
Let me first state that my play-by-play (PBP) data differs slightly from the official record. I excluded yardage gained on returns for TDs in the analysis because a TD precludes SFP. Excluded also was return yardage gained prior to a turnover-fumble.
Concerning INTs, I emphasized that ending opponents’ possessions is most salient and that INT return yardage is a somewhat superfluous stat. INT return yards may be useful to compare playmaking abilities between DBs, although statisticians, teams, and observers might be better served knowing the SFP that resulted from an interception. This notion is definitely applicable for fumble returns where, again, the ending of opponents’ possession is most salient.
Likewise, it is also relevant for rating punt returners. For instance, a player fair catching a punt at his own 9-yard line would be recorded as a fairly unremarkable zero yards (i.e., it is counted in his average PRY). However, the fair catch was probably initiated in the presence of proximal defenders who could have disrupted the impetus of the punted ball at say, the 2-yard line had the returner declined to fair catch. Thus, by fair catching—despite accruing zero yards—the returner in the example would improve his team’s SFP by 7 yards (of course, the defense downing the ball is hypothetical).
The foregoing notion of field position in lieu of yardage is applicable to kick returns as well. For example, let us review the 2014 NFLleading kick-returners by average yards per return. I have Bruce Ellington of the 49ers at 24 returns for 25.9 yards per return;c.f. he ranks about ninth in KR yards. However, Ellington gives his offensive teammates an average starting FP at the ~23-yard line—18th on my list of qualifying players. It may be poor decision making on his behalf or poor block execution behalf of his teammates or that he generally fields kickoffs from superior kickers but we must acknowledge Ellington’s average catch-spot (CS) on KRs was nearly 3-yards into the endzone, ranking third-deepest on my list of qualifying players.1
Although this post is about SFP, the above anecdotes underscore the entanglement of variables involved in appraising performances with yardage accrued. However, Ellington still gained those yards. If we are comparing players (or even coverage units), perhaps, Ellington does rank ninth in KR yards. However, football is about team success and on a given drive, a team is increasingly inclined to success the closer it begins to its opponent’s endzone. Conversely, Ellington’s team did start 3 yards closer to the endzone then would result from him taking more touchbacks.
Moving on, for all teams in the 2014-15 NFL season, I obtained all non-TD turnover-fumble returns, interceptions, kick and punt returns, and field goals missed by opponents using the Pro-Football Reference PBP searchtool. Opponents’ missed FGs include blocks but excludes blocks returned for TDs. For all plays except opponents’ missed field goals, I extracted [a] the spot of the INT, fumble recovery, or catch and [b] the spot at which the player was downed following the return. Computed with those values were [c] return yards or 20 for a touchback and [d] the SFP of the player’s offensive teammates. SFP was scaled such that teams’ own goal lines equaled zero and opponents’ goal lines equaled 100; greater yards indicate better SFP.
| TEAM | TOTAL EVENT COUNTS | AVERAGE STARTING FIELD POSITION BY EVENT | AVERAGE RETURN YARDS BY EVENT | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| KR | PR | FR | INT | oMFG | SFP | KR | PR | FR | INT | oMFG | KR | PR | FR | INT | |||
| KAN | 68 | 76 | 5 | 5 | 5 | 29.3 | 25.4 | 28.7 | 22.4 | 44.0 | 23.6 | 25.4 | 8.6 | 0.0 | 15.2 | ||
| CIN | 78 | 74 | 5 | 19 | 5 | 30.3 | 24.7 | 30.3 | 27.4 | 50.8 | 26.0 | 24.9 | 8.4 | 0.0 | 9.2 | ||
| NWE | 68 | 64 | 7 | 16 | 5 | 30.6 | 22.7 | 32.0 | 36.9 | 51.8 | 29.6 | 22.1 | 7.5 | 0.4 | 11.7 | ||
| DAL | 75 | 66 | 12 | 16 | 2 | 28.9 | 21.1 | 26.9 | 35.5 | 43.3 | 21.0 | 22.3 | 7.3 | 2.6 | 9.3 | ||
| TAM | 81 | 63 | 11 | 11 | 7 | 26.6 | 20.7 | 25.3 | 30.1 | 48.8 | 32.6 | 21.6 | 7.2 | 1.3 | 6.9 | ||
| IND | 79 | 88 | 13 | 11 | 4 | 28.7 | 22.5 | 28.4 | 30.3 | 43.2 | 24.0 | 24.3 | 7.0 | 2.6 | 8.7 | ||
| BAL | 68 | 73 | 12 | 10 | 6 | 28.7 | 23.3 | 30.4 | 32.9 | 48.2 | 27.8 | 22.9 | 6.9 | 4.3 | 9.1 | ||
| JAX | 92 | 74 | 12 | 5 | 4 | 25.7 | 22.1 | 21.5 | 24.3 | 51.0 | 31.8 | 21.9 | 6.4 | 0.8 | 13.0 | ||
| PHI | 83 | 85 | 16 | 9 | 5 | 30.0 | 22.9 | 28.8 | 33.8 | 41.6 | 23.4 | 20.9 | 6.2 | 6.3 | 6.2 | ||
| MIN | 73 | 74 | 4 | 11 | 6 | 27.3 | 25.0 | 25.5 | 15.3 | 49.0 | 30.3 | 21.9 | 6.2 | 0.0 | 8.2 | ||
| STL | 79 | 74 | 11 | 10 | 1 | 28.0 | 22.1 | 28.8 | 32.4 | 42.1 | 35.0 | 22.9 | 5.9 | 3.3 | 10.8 | ||
| BUF | 71 | 86 | 8 | 18 | 7 | 30.2 | 21.3 | 27.0 | 25.5 | 60.4 | 26.9 | 20.6 | 5.9 | 4.4 | 19.2 | ||
| OAK | 94 | 81 | 4 | 9 | 5 | 24.2 | 19.9 | 24.7 | 26.0 | 61.9 | 24.2 | 21.4 | 5.7 | 5.3 | 8.4 | ||
| CHI | 97 | 49 | 8 | 13 | 6 | 25.9 | 21.1 | 27.0 | 15.9 | 43.6 | 23.8 | 20.5 | 5.6 | 2.4 | 10.9 | ||
| SDG | 81 | 66 | 8 | 6 | 2 | 26.4 | 21.3 | 26.5 | 24.1 | 31.7 | 33.5 | 21.1 | 5.5 | 0.0 | 12.0 | ||
| SFO | 70 | 74 | 5 | 21 | 0 | 27.8 | 22.6 | 28.3 | 16.2 | 48.0 | - | 22.9 | 5.5 | 0.0 | 18.8 | ||
| ATL | 89 | 55 | 7 | 15 | 4 | 26.5 | 22.4 | 25.7 | 32.3 | 40.5 | 27.5 | 22.5 | 5.4 | 5.6 | 6.9 | ||
| MIA | 82 | 57 | 10 | 11 | 6 | 31.1 | 24.2 | 25.5 | 21.3 | 50.6 | 23.5 | 23.9 | 5.3 | 0.0 | 17.1 | ||
| DEN | 75 | 84 | 5 | 16 | 5 | 28.9 | 22.6 | 28.2 | 26.0 | 54.4 | 25.2 | 21.4 | 5.3 | 0.4 | 10.8 | ||
| TEN | 89 | 72 | 6 | 11 | 5 | 25.8 | 23.2 | 24.8 | 38.8 | 52.7 | 31.0 | 22.5 | 5.2 | 7.2 | 10.8 | ||
| ARI | 76 | 77 | 5 | 15 | 4 | 26.9 | 19.6 | 24.8 | 20.8 | 51.3 | 32.5 | 20.2 | 5.1 | 1.8 | 10.3 | ||
| NYJ | 85 | 79 | 7 | 6 | 5 | 27.8 | 22.5 | 26.6 | 31.4 | 35.0 | 24.0 | 22.1 | 5.1 | 0.3 | 9.0 | ||
| PIT | 86 | 66 | 10 | 7 | 2 | 25.7 | 20.7 | 24.9 | 32.5 | 48.9 | 29.5 | 21.1 | 5.0 | 3.9 | 18.1 | ||
| NYG | 87 | 74 | 9 | 16 | 2 | 28.2 | 20.7 | 23.7 | 31.6 | 62.1 | 24.0 | 21.1 | 4.9 | 1.5 | 16.6 | ||
| GNB | 79 | 60 | 7 | 15 | 1 | 28.5 | 20.1 | 27.0 | 37.4 | 54.7 | 29.0 | 20.3 | 4.8 | 0.0 | 15.2 | ||
| CAR | 83 | 69 | 13 | 10 | 4 | 27.7 | 21.8 | 25.5 | 32.5 | 45.2 | 25.8 | 21.0 | 4.5 | 2.8 | 19.0 | ||
| SEA | 62 | 81 | 9 | 11 | 2 | 30.5 | 22.4 | 27.7 | 29.0 | 58.2 | 32.5 | 21.4 | 4.2 | 0.0 | 14.2 | ||
| CLE | 72 | 83 | 7 | 18 | 3 | 26.8 | 22.6 | 24.9 | 27.7 | 54.1 | 34.0 | 22.8 | 4.2 | 4.9 | 14.4 | ||
| WAS | 85 | 80 | 9 | 6 | 3 | 25.1 | 21.4 | 22.7 | 29.0 | 45.5 | 18.0 | 20.8 | 4.0 | 2.1 | 5.0 | ||
| HOU | 71 | 82 | 10 | 16 | 2 | 27.7 | 20.4 | 23.5 | 31.9 | 60.6 | 26.5 | 20.7 | 3.8 | 8.7 | 16.6 | ||
| DET | 70 | 81 | 7 | 18 | 4 | 29.9 | 21.1 | 29.4 | 32.9 | 59.2 | 27.3 | 21.8 | 3.8 | 1.8 | 18.7 | ||
| NOR | 86 | 62 | 6 | 12 | 0 | 25.5 | 22.2 | 22.0 | 18.5 | 42.9 | - | 22.3 | 3.0 | 0.0 | 12.5 | ||
| League | Event Counts | Average Field Position by Event | Average Return Yards by Event | ||||||||||||||
| AVG | 79 | 73 | 8 | 12 | 4 | AVG | 27.9 | 22.0 | 26.5 | 29.1 | 50.5 | 27.2 | AVG | 22.0 | 5.6 | 2.3 | 12.3 |
| SD | 9 | 10 | 3 | 4 | 2 | SD | 1.8 | 1.4 | 2.5 | 6.4 | 7.6 | 4.2 | SD | 1.3 | 1.3 | 2.4 | 4.2 |
Table 1 contains 2014-15 distributions, NFL team average SFP and yards gained for each event, and League averages thereof. KRY and PRY are computed with touchbacks equal to 20 yards and no return equal to zero yards. Neither New Orleans’ nor San Francisco’s opponents missed FGs, apparently. There is nothing particularly noteworthy in the table, otherwise.
I also can tell you several things. INTs have the largest impact on the next-SFP when statistically controlling for the initial play spot, the spot at which an INT, fumble recovery, or kick/punt catch occurred, and the yardage gained on the return.2 I can also tell you that for all NFL teams, the majority of SFP yardage is derived from either KR yards or PR yards. Table 2 provides some insight into why this is.
| Majority of Team SFP From | ||
|---|---|---|
| VARIABLE | KR | PR |
| Teams Count | 11 | 21 |
| avg SFP | 27 | 28 |
| avg SFP Unproductive Drives | 24 | 24 |
| avg KR-SFP | 22 | 22 |
| avg Unproductive Drive Yards | 17 | 16 |
| avg Punt Yards | 45 | 45 |
| Opp avg Punt Return Yards | 9 | 9 |
| avg Def. SFP After Unproductive Drive | 24 | 23 |
| Opp avg Unproductive Drive Yards | 16 | 16 |
| Opp avg Punt Yards | 45 | 45 |
| avg Punt Return Yards | 5 | 6 |
| % All Drives Turnovers | 14% | 11% |
| Opp % All Drives Turnovers | 12% | 12% |
| % All Drives End w/ Score | 32% | 35% |
| Opp % All Drives End w/ Score | 39% | 32% |
| win% | 35% | 58% |
Scoring drives are those that ended in TDs or FGs.
In Table 2 we see that the two types of teams perform similarly in most situations. Notably, teams whose majority of SFP is derived from KRs commit TOs slightly more frequently. As an aside, this might suggest that while essentially random, a modicum of TOs may be attributable to offensive ineptitude (albeit, in single season sample). Those teams’ opponents also end drives by scoring considerably more frequently—23% more—than teams whose majority of SFP is derived from PRs. The PR-teams score slightly more frequently.
Most striking in Table 2, though, is the disparity in win percentage. The KR-teams can be expected to win 5.6 games whereas PR-teams can be expected to win 9.3 games. Thus, I conclude that, despite the indelible impact of Devon Hester or the ’84 Seahawks’ 3-4 monster, ultimately, SFP is largely the result of an ungenerous defense supplemented by relatively consistent and careful offensive play.
1 Minimum 1 KR per game scheduled.
2 To accomplish this, SFP was regressed on to play start spot, event spot, and yards gained. The residuals were saved. An ANOVA was performed with those residuals as the dependent variable and event type as the independent variable. A significant effect of event type was found, F(4, 5641) = 17.422, p < .001. Roughly, planned post hoc comparisons indicate the effect of event on SFP could be ranked as INT > FUM > PR > MFG > KR.
