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Eli Manning Isn’t Likely To Complete 70 Percent Of His Passes, Nor Should He Try

One of the biggest talking points of the New York Giants’ preseason has come from comments made last week by Danny Langsdorf, the team’s new quarterbacks coach, in response to a question about Eli Manning’s objectives for the 2014-15 season.

A pass completion rate of 70 percent “hasn’t been done very often, so that’s the ultimate goal,” Langsdorf said. “I think it’s been done eight or nine times, maybe? That’s an impressive statistic in the history of the league. So that’s what we’re gunning for, that 70 percent.”

The story line was repeated by commentators Al Michaels and Cris Collinsworth during NBC’s Sunday night broadcast of the Hall of Fame Game between the Giants and Buffalo Bills, after which it was noted that Manning did, indeed, crack 70 percent — he completed six of seven passes in limited action.

All of this talk might fade as soon as the regular season kicks off and Manning has one of his patented 10-for-24 games. But for now, it looks like the Giants are serious about improving Manning’s completion percentage. Should they be?

On the one hand, Langsdorf is right: The 70 percent completion barrier is an achievement few quarterbacks have broken, and it’s mostly been the realm of Hall of Famers like Joe Montana, Steve Young and Sammy Baugh (a group that will also include Drew Brees someday). Just about any statistical achievement that puts a quarterback in such esteemed company is a desirable goal.

Then again, it’s also incredibly unrealistic to think that Manning is primed to join that group on the accuracy front. Prior to his first 70-percent season in 2009, Brees had a lifetime completion percentage of 63.9 percent; Montana was at 63.2 percent before joining the club, and Young sat at 62.1 percent. Meanwhile, Manning’s career completion percentage is 58.5.

It takes an incredible run of good fortune and locked-in play for any quarterback to hit on 70 percent of his passes, but if we (naively) assume Manning has a “true” completion percentage talent of 58.5 percent, then the binomial probability of him meeting or exceeding the 70 percent threshold in a typical season of 550 pass attempts is about one in 62,042,421. (The 1-in-104,239,853 figure I initially tweeted didn’t include the probability that he would land on exactly 70 percent.)

A legitimate criticism of those numbers is that they’re the product of an oversimplification — Manning, for example, isn’t flipping a weighted coin 550 times, each with the same 58.5 percent probability of heads. Instead, some of his attempts will have a higher chance of completion, and some lower. So if the coaching staff finds a way to reduce the latter and increase the former, it stands to reason that he could shift the odds in his favor. But even if the Giants substantially change the distribution of Manning’s pass attempts and make completions easier, it’s not clear that a new playing style will be what’s best for the team’s passing attack.

There’s a saying, “If you never miss a plane, you’re spending too much time at the airport” — meaning that complete risk-aversion can make things worse than the negative consequences of what someone’s trying to avoid. Manning, as currently constituted, may throw too many interceptions and incompletions, but he’s also one of the league’s best at avoiding sacks and generating net yards (particularly through the air) on a per-completion basis. In some seasons, the downside of this risky style has outweighed the benefit, but in others it has served the Giants well. Interception rate is Manning’s longtime bête noire, but it’s also one of the noisiest of quarterback statistics; when random variance smiles on New York and Manning has a lower-than-expected interception rate, he’s capable of the kind of performance that can win a Super Bowl or two.

(On a related note, there’s evidence from other sports that the more erratic a good-but-not-great player’s performance is, the more championships he can expect to win in his career. This is true for the same reason it’s better for underdogs to use high-variance strategies: Unless they’re the absolute best at something, the only way to beat the field is to introduce random variation into the process. In at least some cases, the luck will break in their favor and they’ll beat the superior opponent through chance.)

Conversely, the list of highest single-season completion percentages contains more than just Hall of Fame-caliber quarterbacks like Brees, Montana and Young. It also includes years like David Carr’s 2006, in which the quarterback completed a lot of short, high-percentage passes that failed to move the ball down the field much. That’s why improving completion percentage is not a foolproof recipe for improving passing efficiency. In terms of relative importance, a one-standard-deviation change in completion percentage (indexed against the league average) is less relevant to adjusted net yards per attempt than a corresponding change in yards per completion, touchdown percentage or interception percentage.

If Manning could guarantee the all-around numbers of a Brees or Montana to go with their gaudy completion percentages, that’s an offer the Giants should take. But it could also be that the quest for a higher completion percentage takes away Manning’s other strengths. As is always the case in football, individual numbers aren’t produced in a vacuum.

Neil Paine was the acting sports editor at FiveThirtyEight.