Going for two should be the norm, a win for mobile QBs

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In their Week 2 game against the San Francisco 49ers, the Pittsburgh Steelers lined up for a two-point conversion after scoring a touchdown. That's not news. What is news is that this happened in the first quarter, after the very first score. This season's new rule -- extra-point kicks are now snapped from the 15-yard line -- has, quite literally, changed the equation. And it could also change the kind of personnel teams employ. First, let's check the math.

A better option

When extra-point kicks were a virtual certainty, the success rate for two-point conversions needed to be over 50 percent to be the better value. But recent two-point conversion rates have hovered between 45 and 48 percent, making the extra point the better value in most circumstances. Of course, in end-game situations, the score can dictate otherwise, but that's the exception to the rule.

Now that extra points are no longer a certainty, two-point conversions are becoming a better option by comparison. We can expect extra points to be successful close to 95 percent of the time based on comparable field goal rates and extra-point rates since the new rule was implemented. That means that the two-point conversion would be just as good an alternative as long as its success rate is 47.5 percent.

0.95 * 1 = 0.475 * 2

Since 2001, two-point conversions have been successful 47.58 percent of the time, right at the point of break-even value. This means that the typical team should be generally indifferent between an extra point and a two-point conversion, and that the decision should be based on the game situation (primarily score and time) and the relative strengths of the units on the field.

But teams that know what they're doing can have even higher success rates, making it the higher value proposition. Over the same period, run plays have been significantly more successful than passes on two-point conversion attempts -- 54.7 percent to 44.8 percent.

This is a classic zero-sum game dilemma, which tells us some very basic things. The more a defense focuses on one type of play, the more vulnerable it is to the other type of play. And the better an offense is at one type, the more often it should employ that type. Offenses should continue to increase the proportion of the more successful option until defenses respond enough and the success rates equalize -- in other words, the typical offense should run more and pass less on two-pointers.

More mobile QBs?

But not all runs are the same. On two-point conversions, it really matters which position is doing the running. Runs by the quarterback are exceptionally successful, with a 65.7 percent scoring rate. Even typical running back handoffs are successful at a 58 percent rate, above the necessary break-even rate even under the old extra-point rules. The overall run numbers are skewed by several unsuccessful "other" ball carriers, typically kickers and holders attempting to make something out of a botched snap.

Unfortunately, the numbers don't make clear whether the QB runs are designed runs, scrambles, or option plays. But one thing is clear: Having a mobile QB helps a team's chances on two-point plays. In fact, as two-point plays become more common, it might be wise for teams without the likes of Cam Newton, Russell Wilson or Colin Kaepernick to carry a fast slash-type player as a two-point specialist.

A Wildcat or option-style athlete who can stretch a defense with his speed but also pass might be the ultimate threat from 2 yards out -- and not just on two-point plays, but anytime an offense is on the goal line. If teams can make room for a specialist like a long-snapper in addition to the two centers they typically carry, it more than makes sense for them to carry a player who can significantly improve their ability to score from within 2 yards.

Time and score should ultimately dictate the choice, but as long as the game is a point-maximization contest, which is typically until the beginning of the fourth quarter, most teams with decent goal-line rushing ability should default to the two-point try.

The NFL may eventually reach a point where the role of each option is reversed. Two-point plays could become the default option, and the extra point would be reserved for end-game situations when just a single point would mean the difference between tying the score or taking a lead. Since 14 percent of all games last season were decided by two or fewer points, that time may come sooner rather than later.