USC held its annual Spring Game on Saturday afternoon at the Los Angeles Memorial Coliseum. And after the 15 allotted practices, it is time to ask: What have we learned about the Trojans this spring?

Let's take a look, four-downs style:

FIRST DOWN: The defense had its best spring of the Lane Kiffin Era, and looks to have similar success in the fall. Throughout the spring, the defense forced turnovers and made plays in ways that haven't been seen since Pete Carroll roamed Howard Jones Field.

The Trojans boast a secondary that is full of NFL-talent (including T.J. McDonald, who could have been the first free safety taken in this month's Draft), a linebacking corps that features three talented sophomores with potentially similar NFL futures and a promising defensive line.

SECOND DOWN: The search for Matt Barkley's backup is ongoing. In 2011, Cody Kessler seemed to be the guy that would get the nod if Barkley were to go down.

This spring, however, it seems fellow redshirt freshman Max Wittek has taken a lead in the race for No. 2. Though Kiffin won't name a leader, Wittek was the first QB off the bench in Saturday's scrimmage and has been for most of spring.

THIRD DOWN: Depth will be an issue at many positions. This isn't groundbreaking, but it is noteworthy. USC is finally entering the first year of scholarship reductions that cap the number of scholarship players on the roster at 75. It was assumed that depth could be a concern, but nothing was for sure until it came time to cross that bridge. This spring the Trojans battled injuries at running back and wide receiver in particular, and began to realize just how thin they actually were.

Of course in the fall, the 2012 recruiting class will arrive and provide some help, but coach Kiffin said after Saturday's scrimmage that depth may cause him to consider limiting tackling in the fall as he did his first season at Troy and in today's Spring Game.

FOURTH DOWN: The new faces on the coaching staff are fitting in nicely. Gone are Joe Barry, Sammy Knight and Ted Gilmore. In are Scottie Hazelton (linebackers coach), Marvin Sanders (secondary) and Tee Martin (receivers).

The players at various points in the spring have raved about their new position coaches, and after their strong showing on Saturday the defensive backs were particularly vocal about Sanders and his ability as a teacher and a motivator.

Check out Will Robinson's recap of Saturday's Spring Game here.

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