Probability, Statistics for Sports

[fletch]

With the NFL regular season finished and the playoffs beginning, I thought I would do a post on football statistics.  In contrast to hockey’s (mostly) continuous action, football has discrete plays (like baseball).  In addition, football has a basic unit, the yard.  Similar to baseball, there is an avalanche of data available for offenses, defenses, and special teams.

https://www.nfl.com/stats/player-stats/

 

For field goal kickers, a benchmark is percentage of extra points and field goals made.  This can be subdivided by length, percentage of field goals made over 50 yards, from 40-49 yards, etc.  Field goal kickers have gotten more accurate over time.

http://www.footballperspective.com/field-goal-rates-throughout-nfl-history/

 

For punters, average yards per punt (yards in air) and net yards per punt (subtracts return yards) are important.  Plus, punts downed inside the 20 is a good metric, as the closer an offense starts to their own end zone, the greater the advantage to team defenses.

 

In the 1980s when I first started watching football, the benchmarks for skill positions was 1000 yards rushing for running backs, 1000 yards receiving for wide receivers and elite tight ends, and 3000 yards passing for quarter backs.  Partly because of rules changing improving player safety, more varied play-calling, and other factors, offenses have become more prolific.

https://www.eldo.co/a-complete-history-of-nfl-points-scores-and-scoring.html#:~:text=After%20several%20decades%20of%20volatility%2C%20NFL%20scoring%20has,two%20decades%2C%20and%20are%20now%20near%20all-time%20lows.

 

Generally, this is due to increased efficiency in the passing game.

https://www.pro-football-reference.com/years/NFL/scoring.htm

 

Because of changes in the games, the benchmarks of 1000 yards rushing for running backs, 1000 yards receiving for wide receivers and elite tight ends, and 3000 yards passing for quarterbacks have changed.  In the 1980s, it was common for one running back to get most of the carries for most of the teams.  Now more teams are rotating running backs, to keep a fresh ground attack, and to develop reps for multiple players given injury risk.  Plus, running backs have become more involved in the passing attack with check downs and other plays.  The link below is a little more nuanced – for all-time leaders, look at yards receiving per game for McCaffery and Kamara versus retired players.

https://www.statmuse.com/nfl/ask?q=most+receiving+yardsby+a+running+back+all-time

 

Average passing yards have increased by year.  Player safety rules to help protect quarterbacks and defenseless receivers, as well as increases in the penalties for pass interference and illegal defensive contact, have favored offenses, particularly with the passing attack.

https://www.pro-football-reference.com/years/NFL/passing.htm

 

For defensive players (especially linebackers) tackles are a good benchmark.  For a season, I look at players with greater than 100 tackles.  Also, sacks, tackles for loss, forced fumbles, and interceptions are key metrics.  Sacks and tackles for loss make it more difficult for offenses to make first downs and keep possession.  Turnovers (fumbles and interceptions) gain your offense possession, often with good field position.  Ideally, your defense can score on the turnover.  Safeties are especially rare, and in addition to the two points, give the ball back to your offense after a return.

 

Special teams (punts and field goals) often get less fan attention.  Average return yards per punt return, average return yards per kickoff are good benchmarks.  A special teams touchdown (similar to a defensive touchdown) is a big momentum swing for the team scoring.  A blocked punt or kick also usually helps field position, and can result in a special teams touchdown.  A blocked field goal attempt prevents your opponent from scoring.

 

I’ll take a break before having a look at some advanced NFL statistics.

[fletch]

First, link for advanced stats for NFL.  I won't cover every stat on the site, so worth exploring on your own.

https://www.pro-football-reference.com/years/2022/advanced.htm

Passing

Intended air yards (IAY) – air yards on all pass attempts, whether complete or incomplete

Intended air yards per passing attempt (IAY/PA) – average depth of target, whether completed or not

Completed air yards (CAY) – total yards completed passes travelled in the air past the line of scrimmage before being caught

Completed air yards per completion (CAY/Cmp) – yards the ball traveled in the air past the line of scrimmage prior to a completion

Pass yards after catch (YAC)

Pass yards after catch per completion (YAC/Cmp)

 

Rushing

First downs rushing (1D)

Rushing yards before contact (YBC)

Rushing yards before contact per attempt (YBC/Att)

Rushing yards after contact (YAC)

Rushing yards after contact per attempt (YAC/Att)

Broken tackles (BrkTkl) – Broken tackles on rushes

Rush attempts per broken tackle (Att/Br)

 

Receiving

First downs receiving (1D)

Yards before catch (YBC) - total yards passes traveled through air before being caught

Yards before catch per reception (YBC/R)

Yards after catch (YAC)

Yards after catch per reception (YAC/R)

Average depth of target (ADOT) – average depth of target when targeted, whether completed or not

Broken tackles (BrkTkl) – Broken tackles on receptions

Receptions per broken tackle (Att/Br)

Dropped passes (Drop)

Dropped passes per target (Drop%)

 

I’ll do a separate post for defense.

[fletch]

Link for advanced stats for NFL defenses.

https://www.pro-football-reference.com/years/2022/opp.htm

 

Play (Ply) = offensive plays = pass attempts + rush attempts + times sacked

Yards per play (Y/P) = (rush + pass yards) / (pass attempts + rush attempts + times sacked)

Turnovers (TO) = takeaways

Fumbles recovered by team (FL)

First downs allowed (1D) 

First downs allowed by passing (1D) 

First downs allowed by rushing (1D) 

Interceptions gained (Int)

Net yards gained per pass attempt (NY/A) = (passing yards - sack yards) / (pass attempts + times sacked)

Rushing yards per attempt (Y/A)

Penalties (Pen)

Penalty yards (Yds)

First downs by penalty (1st Py)

Percentage of drives ending in an offensive score (SC%)

Percentage of drives ending in an offensive turnover (TO%)

Expected points contributed by defense (EXP)

Blitz percentage (Bltz%) = Blitzes per dropback

Hurray percentage (Hrry%) = QB hurries per dropback

Quarterback knockdowns per passing attempt (QBKD%)

Pressure percentage (Prss%) = (hurries + knockdowns + sacks) per dropback

Missed tackles (Mtkl)

Yards per punt return (Y/R)

Yards per kickoff return (Y/Rt)

Points allowed per game (Pts/G)

Red Zone percentage (RZPct) = percent of time opponent scores a touchdown when entering the red zone (20 yard line or closer)

Third down conversion percentage (3D%)

Fourth down conversion percentage (4D%)

Average drive points allowed (Pts)