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USC offensive coordinator Graham Harrell was asked this week which running backs would be healthy and active for spring practice.

It's perhaps become instinct to not assume full strength from the unit, as no position group on the team incurred more injury setbacks in 2019.

"That's a good question. I don't know," Harrell responded. "I'll be interested to see who trots out there. We haven't really discussed who all is going to be cleared for spring. Again, I do think we have tough guys and guys who want to be out there, but we have to be smart about where they are. If they're healthy, they'll be out there. If they're not, especially in the spring, we'll do everything we can to get them reps and improve them but also be smart about [making sure] we get them back for next fall."

At some point, though, the Trojans are eventually going to have an interesting situation to manage -- a good dilemma, for sure -- when senior Stephen Carr, redshirt senior Vavae Malepeai, redshirt sophomore Markese Stepp and sophomore Kenan Christon are all full-go. It's a quandary that doesn't require clarity until the fall anyway, but it will nonetheless be talked about this spring.

What do the Trojans do if they have all four of those options to choose from?

Harrell didn't get that question Tuesday, but he will eventually.

Malepeai essentially operated as USC's lead back last season when healthy -- before requiring minor knee surgery that cost him five games. Prior to the injury he led the team in carries and total RB touches by a clear margin each of the first four games, tied for the lead in carries and led in RB touches the fifth game and then was limited in the sixth game before finally admitting his injured knee was a real problem.

The veteran is a favorite of running backs coach Mike Jinks, the kind of player who does everything right in practice and has the full trust of the decision-makers. He finished with a team-high 503 rushing yards and 6 touchdowns (plus 15 catches for 70 yards and 1 TD) despite missing all that time, but his 4.8 yards per carry was the lowest of the four running backs by a good margin (0.7 yards to be precise).

Carr, meanwhile, is a senior who maintains a high profile despite playing a limited role last season, when he rushed for 396 yards and 5 TDs on 5.5 YPC in addition to 22 catches for 143 yards and 1 TD. He missed three games with a sprained ankle, but he only received double-digit carries once (in a game Stepp missed and Malepeai was eased back into action). Carr's health and whether he's ever regained the burst that made him a budding star as a true freshman years ago are always part of the discussion, but he still brings plenty to the table as a plus pass-catcher out of the backfield, a willing blocker and shifty back who still can juke a defender out of his shoes in the right situation. He led the team overall with 26 tackles avoided on his 72 carries, per PFF College's data.

But that all leads back to the familiar debate from last season.

Feeding those veterans limited the opportunities for Stepp, who looked like arguably the Trojans' best running back last fall while averaging a team-best 6.4 YPC (307 rushing yards and 3 TDs overall). He's the most unique of the Trojans' backs, a bulldozing force who didn't necessarily need wide lanes -- or any lanes -- to plow forward for positive yards or extra yards. He averaged a team-best 4.11 yards after contact per carry, according to PFF, though Carr wasn't far behind at 3.38, followed by Malepeai at 2.88 and Christon at 2.25.