Here's the scary part for anyone who doesn't wear crimson. The YPC rates as backups almost all improved when the players moved to the primary back role. Lacy was never going to sustain that 7.09 YPC rate as the starter, particularly because a line of nine carries for 161 yards against North Texas skewed it way upwards. Take out that day and he had a 5.96 YPC rate as the backup. That sounds better, until you realize that it means he also basically increased his YPC rate when he slid into the starting spot just like the other guys did.
So let's put this all together. What are we looking at for Yeldon in 2013?
I don't think he'll end up with fewer carries than Coffee did in 2008, which was 233. He probably won't match Richardson's 283 carries in 2011 unless the backup situation ends up as bad as Saban was trying to make it sound. Because numbers that end with fives and zeroes sound the best, let's set his range at 235 to 270 carries. That span will put him between Coffee's 2008 and Ingram's 2009 in terms of times toting the ball.
Given the track record, Yeldon's yards per carry rate might actually improve from where it was last season. He could end up roughly matching Lacy's 6.5 YPC rate as the starter. Past results do not necessarily indicate future performance, however, and his rate could fall due to offensive line issues, the defenses he'll face, or something else like that. We'll set the floor at 5.9 yards per carry, which is just below what Coffee, Ingram, and Richardson did in the primary role.
At the low end of the range, it comes out to 235 carries for 1,387 yards (5.9 YPC). At the high end of the range, it comes out to 270 carries for 1,755 yards (6.5 YPC). Right in the middle is 251 carries for 1,556 yards (6.2 YPC). The low end would probably be a disappointment given Yeldon's high expectations for this year, as it wouldn't be that much more than what he did in 2012. The high end would be a pretty heroic effort and would almost certainly get him to New York for the Heisman ceremony.
Right down the middle is probably about right for expectations, and the fact that 1,500 yards at a 6.2 YPC rate over 250 carries sounds reasonable tells you just how good this guy is.