Spring position preview: OLs

We’re doing position-by-position previews in the weeks leading up to spring practice, breaking down the depth chart for one position group each day, paying special attention to things that can change in the spring.

We’ve looked at the quarterbacks, running backs, receivers and tight ends so far. Today, we analyze the offensive linemen.

This was a problem position group last year for the Trojans, at least until midway through the 2011 season. There was a ton of uncertainty over the guard spots at this point last year, and it largely remained until the final weeks before the regular-season opener.

That won't be the case this year, even though USC is replacing star left tackle Matt Kalil.

The middle three linemen should all be returning starters, with Marcus Martin and John Martinez manning the left and right guard spots and Khaled Holmes at center. Then Aundrey Walker, a sophomore, is going to start the spring at right tackle, and Kevin Graf, a fourth-year junior, is going to do the same on the left side.

That is the most likely alignment come September, too, although it's also likely Walker will get a chance at some point to unseat Graf on the left side. How early that chance will come -- and how many chances there will be -- is still uncertain.

What's there to watch this spring, then? A few things, actually, with maybe the most interesting being exactly how much weight Walker has lost since enrolling at USC. He was listed at 375 pounds all of last season, a weight which reportedly came from his official visit in January 2011. Now, Lane Kiffin is saying he's dropped 60 pounds to 315.

That's a big number, but, if true, could mean he gets an almost-immediate chance to unseat Graf. Even at 6-6 and 300-something last year, it was easy to see Walker's natural athletic ability and quickness on the line. Now that he's dropped a significant amount of weight, it should get even easier.

Linemen who have significant quickness at 6-6 and 300-plus pounds tend to play left tackle, especially at the college level.

Another thing to watch: How did Martin's offseason weight-loss program go? He was listed at 340 pounds last season but has appeared slimmer in winter conditioning workouts.

And, one last thing to note: Unless players leave unexpectedly early for the NFL next offseason, it's likely USC will again return four starters with a combined seven years of starting experience on the offensive line in 2013.

Check back Tuesday for the defensive linemen.