Vikings

Why Mike Zimmer Obsesses Over Time Of Possession

Photo Credit: Robert Hanashiro (USA TODAY Sports)

Throughout the 2020 season, there has been a focus on the Minnesota Vikings’ time of possession:

And Mike Zimmer has emphasized time of possession all season:

 

But what is the point of time of possession? The idea we’re most familiar with is to keep the ball so your opponent doesn’t get it. Scared of Russell Wilson? Keep the ball out of his hands as much as possible. Run the ball, chew clock, and keep him on the bench, right? But when held up to scrutiny, those things don’t have much to do with time of possession at all.

Drives alternate in the NFL, no matter how long those drives are. If the Vikings have an eight minute touchdown drive, the Green Bay Packers still get an opportunity. If they score in 45 seconds, the scoreboard would be tied while time of possession is lopsided. You can shorten the game and deny your opponent possessions, but not without denying yourself possessions as well. Unless you’re near the end of a half, you cannot deny a possession. You can only delay it.

On the whole, there isn’t much an offense can change about its strategy to help its defense. Whatever gets more yards, more points and better field position can help the defense. But that just encourages good offense, not necessarily specific strategy. If the offense plays well, it can help the defense — but you would assume they already planned on doing that.

If we want to measure how well the offense sets up the defense, we can turn to average starting field position, which is available for free at Football Outsiders. For what it’s worth, the Vikings defense has the worst starting field position in the league, with the average opposing possession starting around the 35.

Time of possession gets a reputation as a proxy for fatigue. Grind enough clock, and the defense gets tired. Go three-and-out with three consecutive incomplete passes, and broadcasters will groan on the defense’s behalf. How laborious it must be to trot back on the field after just 10 seconds of offensive possession. Contrary to (astoundingly) popular belief, defenders can rest when the clock is stopped, too.

Take the Week 3 game between the Atlanta Falcons and Chicago Bears. During the umpteenth Falcons meltdown, the Bears scored a touchdown to pull the game within three points. Atlanta then had a five-play, 22-second series that culminated in a punt. However, the Falcons defense rested for 7:15 of real life time (not including the commercials that NFL Gamepass cuts out); an eternity to catch your breath.

Fatigue is not very well-studied in the NFL. Common sense tells us that players get tired as the game goes along, but these players are hyper-conditioned athletes at the peak of human performance. A three-hour game session is no doubt fatiguing, but what if players are in good enough shape to handle it? A recent Big Data Bowl study asked if players get slower as a game wears on and found some relationship. The more plays a player plays, the more likely they are to slow down, but that also varied from player to player.

If we assume that playing more plays would lead to fatigue, then we can use play count to measure that effect. Since NFL games guarantee each team an equal number of possessions, we can instead look at how many plays a defense runs on an average drive. That’s also at Football Outsiders. They have the offensive version too, to give a better sense for rest time than the stop-and-start of the game clock.

Every time Zimmer talks about time of possession, he references “shortening the game.” If you can chew up clock, you can limit the number of possessions in the game. There is some merit to this, even if it sounds zero-sum. For example, it requires fewer stops on defense. That comes at the cost of fewer offensive opportunities, but a defensive-minded head coach like Zimmer is happy to take that trade.

Imagine a seven-game NBA playoff series. Upsets can happen over one or two games, but more or less, the better team wins the series. Compare that to the NFL playoffs, where a single fluky game can cause a middling 9-7 team to upset the only 16-0 team in history. Tom Brady would have liked the 2007 Super Bowl to be a best-of-three, but Eli Manning would likely disagree. This is the true value in shortening the game. If you’re the underdog, only high-variance, fluky outcomes will end in wins. As a heavy favorite, you want the most predictable thing to happen.

An average game has 10 possessions per team. The Packers had eight possessions in Sunday’s game, the Vikings had seven. That’s partially thanks to the wind dissuading both teams from throwing deep, but also speaks to the strategy Zimmer constantly cites. The Packers only had six possessions that weren’t pressed tight against the clock. Their third possession started with less than 30 seconds in the half, and their final possession started with less than a minute, and they had no timeouts.

That meant that the Vikings, who scored on four of their seven possessions, only needed three stops in neutral situations to win the game. Put another way, the Vikings had the advantage of a short clock on 25% of their defensive possessions. A more standard game could have required five or six of 10 stops against Aaron Rodgers and the Packers, or six of 10 scores against Mike Pettine’s defense. The Vikings didn’t win against Green Bay sustainably, but because of their clock-chewing nature, they didn’t have to.

Time of possession isn’t the best way to examine defensive fatigue or the effects of complementary football. But in a season where the Vikings will be underdogs more often than not, grinding the clock should prove advantageous.

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