USC kicked off spring ball on Tuesday, the first practice under new head coach Lincoln Riley. It’s officially a new era.

Riley and the Trojans have a lot to do in just 15 practices. For a roster that has seen so much change in the months since he took over the program, it would appear there’s more still to come. USC has a good deal of flexibility with the roster, Riley has said, but it is in a spot where it needs talent at the top and depth to fill in the gaps.

“We’ve got a lot of roster work to do between now and the first day of camp and the first game,” he told reporters after practice, per The Athletic’s Antonio Morales. “There are going to be double-digit additions. There’s no question about it.”

Quarterback might seem like a spot that’s already settled—and make no mistake, Caleb Williams will be the guy—but the Trojans only have two healthy scholarship quarterbacks at the moment.

“It’s not ideal,” Riley said, per Morales. “I certainly wouldn’t take that off the table that we would look at adding somebody. Honestly, with our roster right now you could say that with any position that there is.”

At the beginning of March, quarterback Mo Hasan announced that he’d ruptured the Achilles tendon in his right leg and would be sidelined for the near future. With transfer departures from the top two guys last season, it left the Trojans with Williams and Miller Moss as the only two scholarship options for the team this spring period.

Riley and Co. will hope for good health, and with quarterbacks, they can do a bit more to protect them than with other spots on the team. USC also has two walk-on quarterbacks on the roster in redshirt senior Brad Aoki and redshirt sophomore Isaac Ward.

But adding depth to the room might not be easy. Quarterbacks who jump into the portal after spring ball aren’t typically looking to move to a place with an entrenched starter to be a “break in case of emergency” option.

You can see Riley’s full post-practice session with reporters here.