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Adjusted Completion Percentage, Part 2

Last summer, I discussed that while completion percentage is a bad statistic, there’s one simple way to improve the metric: include sacks in the denominator.

If a quarterback takes a sack, that is *worse* than an incomplete pass, but it is *better* for the quarterback’s completion percentage. That is Just Plain Wrong.

As it turns out, this really impacts Peyton Manning and, to a lesser extent, Drew Brees. In 2003, Manning led the NFL in both completion percentage (67.0%) and adjusted completion percentage (64.9%). Technically, Manning didn’t win any other completion percentage crowns, although PFR gives him a tie in 2012. 1 However, he won the adjusted completion percentage crown a whopping five more times in his career: 2004, 2006, 2008, 2012, and 2013.

Brees has three completion percentage crowns (a fourth may come this season), but two more adjusted completion percentage titles. From 2003 to 2016, Manning won six AC% titles, Brees won give, and the rest of the league (Cousins, Brady, Palmer) won just three. In fact, from the six-year period covering 2008 to 2013, Manning and Brees won all of the adjusted completion percentage crowns.

The full list of leaders in each year since the merger are presented below, along with where that quarterback ranked in raw completion percentage (using a minimum of 224 passing plays per 16 team games for both metrics):

QuarterbackYearTeamAdj Cmp%DropbacksAct Cmp%Cmp% Rk
Drew Brees2016nor67.3%70070%2
Kirk Cousins2015was66.6%56969.8%1
Drew Brees2014nor66.3%68869.2%2
Peyton Manning2013den66.5%67768.3%3
Peyton Manning2012den66.2%60468.6%3
Drew Brees2011nor68.7%68171.2%1
Drew Brees2010nor65.6%68368.1%1
Drew Brees2009nor68.0%53470.6%1
Peyton Manning2008clt65.2%56966.8%3
Tom Brady2007nwe66.4%59968.9%1
Peyton Manning2006clt63.4%57165%3
Carson Palmer2005cin65.3%52867.8%1
Peyton Manning2004clt65.9%51067.6%3
Peyton Manning2003clt64.9%58467%1
Chad Pennington2002nyj65.3%42168.9%1
Kurt Warner2001ram64.2%58468.7%1
Kurt Warner2000ram64%36767.7%1
Kurt Warner1999ram61.6%52865.1%1
Brett Favre1998gnb58.9%58963%1
Steve Young1997sfo61.6%39167.7%1
Troy Aikman1996dal61.3%48363.7%2
Steve Young1995sfo63.3%47266.9%1
Steve Young1994sfo65.9%49270.3%1
Troy Aikman1993dal64.8%41869.1%1
Steve Young1992sfo62.2%43166.7%1
Steve Young1991sfo61.6%29264.5%3
Jim Kelly1990buf59.8%36663.3%1
Joe Montana1989sfo64.7%41970.2%1
Dan Marino1988mia57.8%61258.4%8
Joe Montana1987sfo63.3%42066.8%1
Joe Montana1986sfo59.9%31962.2%3
Dan Marino1985mia57.4%58559.3%5
Dan Marino1984mia62.7%57764.2%3
Ken Anderson1983cin61.5%32266.7%1
Ken Anderson1982cin65.1%33570.6%1
Joe Montana1981sfo60.5%51463.7%1
Joe Montana1980sfo61.1%28864.5%1
Dan Fouts1979sdg59.5%55862.6%1
Bob Griese1978mia58.5%25363%1
Fran Tarkenton1977min55.4%28060.1%1
Ken Stabler1976rai62.6%31066.7%1
Fran Tarkenton1975min60.4%45264.2%1
Ken Anderson1974cin58.5%36464.9%1
Ken Stabler1973rai55.4%29462.7%1
Norm Snead1972nyg58.9%33360.3%1
Virgil Carter1971cin58.7%23562.2%1
John Brodie1970sfo57.8%38659%2

As noted in the original post, Dan Marino in 1988 is the most extreme example, as he led the NFL in AC% but ranked just 8th in raw completion percentage. Marino never led the NFL in completion percentage, but led the league in adjusted completion percentage in ’84, ’85, and ’88, and ranked 2nd in 1986.

What stands out to you?

  1. Technically, he lost it to Matt Ryan that year once you go out to two decimal places, 68.62% to 68.61% (although if you include sacks in the denominator but keep the minimum at 224 passing plays, Alex Smith was the completion percentage champion in 2012). []