Not so Tailback U.?

USC comes into this season as the No. 1 team in the nation but there are several stumbling blocks on the road to a national championship and this week we take a look at five key concerns for the Trojans.

It’s hard to imagine USC being a national championship contender without a deep backfield but that’s exactly the position the Trojans are in coming into this season.

USC coach Lane Kiffin has said on numerous occasions that the number one concern for this team is the tailback position and particularly the lack of depth at that position. The Trojans go into camp with senior Curtis McNeal as the starter, after he ran for 1,005 yards last season, but there’s a major drop in experience and production after McNeal. Next up on the depth chart is sophomore D.J. Morgan, who has a grand total of 163 yards on 43 carries in his career.

The Trojans are hoping that the 5-foot-7, 190-pound McNeal, who has only played two seasons in his USC career, will be durable enough to last the season unscathed and carry the bulk of load in the backfield.

Kiffin moved sophomore linebacker Tre Madden to tailback in the spring, but Madden suffered a knee injury that will sideline him in 2012.

He also moved sophomore receiver George Farmer to tailback last season before pulling the plug on that experiment.

Not only is USC thin at running back, they must also find a new starting fullback after losing Rhett Ellison. That spot will likely be filled by freshmen Soma Vainuku and Jahleel Pinner, but again, experience is a major question mark there with two players seeing their first game action.

The backfield has been such a concern that Kiffin is now trying to convince tailback Silas Redd to transfer to USC after the NCAA announced its sanctions against Penn State. Redd, a junior, rushed for 1,241 yards and seven touchdowns last season as Penn State’s featured back. The NCAA announced that Penn State players can transfer to other programs with no restrictions and won't have to sit out a season.

If Redd transfers to USC he would instantly compete for the starting job and at the very least give the position some much needed depth and experience. If not, USC will have to cross its fingers and hope McNeal stays healthy at running back and that a couple of freshmen grow up fast at fullback.