Ask Farmer: Does a prevent defense really work?

Have a question about the NFL? Ask Times NFL writer Sam Farmer, and he will answer as many as he can online and in the Sunday editions of the newspaper throughout the season. Email questions to: sam.farmer@latimes.com.

I have been observing college and pro football for a long time. There have been lots of changes. One thing that has not changed is the frequent use of the “prevent” defense. My observation is that more times than not this defense prevents the team that deploys it from winning. Why is it still used?

Dick Terrill, Torrance

Farmer: I posed this question to Hall of Fame coach John Madden.

“The only time that fans don’t like prevent defense is when it doesn’t work,” Madden said. “When it does work, you don’t even notice it. It’s like good officials and a well-officiated game, you don’t notice them at all. If you have poor officials, then the whole game is based on officiating.

“If the prevent works, no one ever talks about it or writes about it or mentions it.”

That said, Madden never liked the prevent.

“I thought it made the players play too conservatively,” he said. “Pretty soon they’re aware of everything and doing nothing. But I bet if you did the statistics on it, the amount of times that you use it and it works and you win the game would be a pretty high percentage.”

Indulge me in a funny aside: The late Mike Heimerdinger, a well-traveled offensive coordinator, used to say he was jealous of his defensive counterpart because, while everyone thinks they know offense, few fans spend the time to grasp the complexities of defenses.

“I know my wife never sits in the stands and hears, ‘Hey, why’s the defense in two-deep?’ ” he told The Times in 2003, when he was with the Tennessee Titans. “The only time you ever hear a fan complain about a defense is when they’re in the prevent, and that’s probably because TV announcers are always talking about how they hate the prevent.”

It’s when their team is on offense that fans break out the imaginary chalkboards.

“If I call a run, half the stadium thinks I should be passing,” Heimerdinger said. “If we throw an incomplete pass, people think I’m an idiot.”

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What impact does a successful two-point conversion pass have to the quarterback rating? Is it just another completion or like a mini-touchdown?

Paul Murray, La Cañada Flintridge

Farmer: Actually, it doesn’t count as either. According to the guidelines for NFL statisticians: “No rushing, passing, receiving, interception, fumble or sack statistics shall be credited during an extra-point attempt. However, penalty yardage, if assessed, is recorded as if during a scrimmage down.”