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: When filling these spots, will teams be reloading or rebuilding? Your humble Pac-12 blog takes a look at which players from the top-25 player countdown need to be replaced entering the 2016 season.

Big shoes: Su’a Cravens

Cravens arrived at USC as one of the nation’s most sought-after safety prospects and left a potential first-round pick at outside linebacker. His stats as a junior underrepresent how important he was to the team’s defense, but he still led the team with 86 tackles and 15 tackles for loss and was the only offensive or defensive player in the Pac-12 to earn first-team all-conference accolades the past two seasons.

He was a rare talent in that he was athletic enough to cover receivers man-to-man and physical enough to be effective in run support. There have been a few players to come through the conference with similar attributes the past few years, but outside of Shaq Thompson, Myles Jack and maybe a few others, what he does is not easily emulated.

Stepping in: Clancy Pendergast’s return as defensive coordinator means the Trojans will employ a 5-2 base defense, as they did in 2013, and there won’t necessarily be a player who occupies the role Cravens held last season. That said, even if Justin Wilcox was still around, there wouldn’t be a single player capable of mimicking how Cravens was used.

Osa Masina and Porter Gustin, both of whom had promising true freshman seasons as linebackers, are now listed at defensive end and have the ability play the hybrid role off the edge that Pendergast looks for. Redshirt senior Jabari Ruffin (33 career tackles), true freshman Oluwole Betiku, and redshirt freshmen John Houston Jr. and Christian Rector are some of the other options. Scott Felix would be, too, but his status remains in limbo as a result of a personal issue.