In 2012, he was darn near unstoppable.
This week, Advanced Stat of the Week will look at running back success rate. Success rate is one of the most important ways to judge the true effectiveness of a runner. Consider the following two hypothetical runners.
Runner A gets the ball on the 20-yard line. He immediately rips off a 40-yard run, moving the ball down to the opposing 40. The next three runs, he's stopped for no gain and his team punts. Runner A has 40 yards and 10 yards a carry on that drive.
Runner B gets the ball on the 40 and picks up 3.5 yards each time he sees the ball, without fail. This hypothetical super-back would be the league MVP because, despite averaging just 3.5 yards a carry, you could give him the ball every down and he would always get a first down.
Success rate illustrates that a runner's ability to move the chains is his most important quality. "Boom and Bust" backs can be exciting, but carries for negative yards are drive killers. Long runs thrill fans, but consistent gains are more valuable.
The Football Outsiders calculate success rate roughly in terms of the percentage of yards gained by the runner each down. On first down, a back needs 40 percent of the yards his team needs for a first down. On second down, that jumps to 50 percent. On third and fourth down, a run is only successful if the back gets 100 percent of the necessary yards.
In terms of success rate, a three-yard run on 1st-and-10 is not successful. A three-yard run on 2nd-and-5 is successful. An eight-yard run on 3rd-and-10 is not successful. This sliding scale helps account for meaningless yards that a back accrues during the course of the game. Seven-yard gains on a draw on 4th-and-20 don't often mean much in the course of a football game, and success rate shows us that. A running back should be looking for a success rate north of 50 percent.
Foster had one of the best all-around seasons in football in 2012. His yards per carry were down, but in many ways he was more effective than he had been in 2011.
While his overall success rate peaked his rookie year at 59 percent, the steady slide backward reversed itself.
Foster finished the year at 47 percent, good for 27th in the league. That's a nice improvement from 2011's relatively weak 44 percent. While not an elite number, it's also just one of many metrics you can use to judge a runner. It should never be taken in a vacuum.
What does it mean in terms of actual game carries?
In 2011, Foster had 122 "successful" runs.
In 2012, he had 165.
Combined with his increased workload, Foster's improvement translated to more than 40 more successful runs on the year.
That's two or three times per game that he picked up the first down or put the team in solid position to get first downs.
For a back to lead the league in carries and still post an improved success rate is a real accomplishment. Down the stretch, and especially in the playoffs, Foster demonstrated that he is an elite back, and the real workhorse of the Houston offense.
Nothing he does may ever match his All-Pro 2010 season, but there's no question that Foster is one of the best and most valuable runners in football.