Biggest shoes to fill: USC

Players come and go.

In a perfect world, the teams only have to reload, not rebuild. But following this season, there are a lot of shoes that need to be filled due to early departures and expected graduations.

That leaves the question: Will these spots be reloading or rebuilding? Your humble Pac-12 blog takes a look at some of the biggest shoes that need to be filled entering the 2015 season.

USC Trojans

Biggest shoes: DT Leonard Williams

USC must replace three first-team All-Pac-12 performers, but the two departures on offense -- RB Javorius Allen and WR Nelson Agholor -- won't provoke many headaches. The Trojans are typically deep at the skill positions, and that will be the case in 2015, at least if young players continue to develop and/or live up to their star-billing. As for Williams, you can't easily replace a likely top-five NFL draft pick with one guy, particularly at a premium D-line spot. It's not completely about numbers either. Williams ranked second on the Trojans with 80 tackles, with 9.5 tackles for a loss and a co-team-high seven sacks. He also collected an interception and forced three fumbles. Those are good but not eye-popping stats. The larger issue with Williams was every offensive coordinator started preparation for the Trojans with, "What the heck are we going to do with that disruptive beast?" USC's defense was surprisingly inconsistent last year, and you could have wondered where it might have been without Williams. That reasonably becomes a key question for the Trojans, whom many are touting as a College Football Playoff contender, heading into a season when the speculation will be realized.

Stepping in: Claude Pelon, Delvon Simmons, Greg Townsend and a freshman

The most predictable starting D-line for USC would have Simmons and Pelon manning the DT/DE spots and Antwaun Woods or Kenny Bigelow at NT. Simmons was more productive last year with 44 total tackles, while Pelon was more of a playmaker with six tackles for a loss and 2.5 sacks. Townsend, Malik Dorton, if he's not moved to an outside LB spot, and an incoming player -- Rasheem Green, Jacob Daniel, Noah Jefferson, Christian Rector or Kevin Scott -- would add depth. It's also possible that LB Jabari Ruffin could get at look at DE. Don't be surprised if more than one or two true freshmen see action. While coaches always play for the present, the USC D-line will be senior-heavy next fall and the next generation needs to be ready for 2016. None of these potential combinations will equal one Williams, but the hope is increased depth will make for a more potent front in its totality.