When Lincoln Riley took the reins of a USC program in desperate need of a rebuild, no one expected a new foundation to be laid overnight. Still, when Riley was asked in November how quickly he could turn around the Trojans, he didn't try to limit expectations.

"In this day and age, I think it can happen quickly, I do," Riley said.

Fast forward nine months — and 20 transfers — later, and USC enters camp as one of the most intriguing roster experiments in college football, a team rebuilt almost entirely through the transfer portal. Torn down essentially to the studs, the Trojans return this season with a new coaching staff, a new quarterback, a new backfield, two new potential All-American receivers, a new left tackle, a new corps of linebackers and a handful of new faces in the secondary.

What Riley has already built over the course of a single offseason will stand as an early case study for program building in the age of the transfer portal. Can a team that completely unraveled be completely transformed overnight? We'll know soon enough.

As USC opens its first training camp of the Riley era on Friday, plenty of other pressing questions need to be answered first:

What should we expect from quarterback Caleb Williams and new top receiver Jordan Addison?

They grew up just an hour apart in the Washington, D.C., area, but Caleb Williams and Jordan Addison didn't know each other well until this past spring, when Addison, the 2021 Biletnikoff Award winner, suddenly became available in the transfer portal, and Williams, USC's new quarterback, turned his attention to recruiting the reigning top receiver in college football.

"I was in his ear," Williams said last week. "I think I texted [linebacker] Shane [Lee]. I was like, 'Text this kid.' I think it was 15 of my teammates I had text Jordan. Like, guys, 'We're going to need him to go win some big games.' That's how important Jordan was. That's how important all these guys I tried to help support and get here to come play with me."

None may be more crucial than Addison, who gives USC's offense a deep threat unlike any other in college football. Addison scored 10 touchdowns of 20-plus yards at Pittsburgh last season. At USC, teammates are already marveling over his speed.

"He runs like 23 mph, which is crazy," Williams said. "He can do just about anything."

We don't yet know how Riley plans to deploy him. But for the Trojans, it's been quite some time since a quarterback-receiver connection has looked this promising.

How much have new transfers helped the defense?

There's no question USC will be loaded on offense, with a Heisman contender at quarterback and a bevy of new weapons around him. Consider that Riley, in seven seasons as coordinator and coach at Oklahoma, never once finished outside of the top eight nationally in scoring offense, and it's easy to envision the Trojans scoring plenty of points in plenty of ways this fall.

The crippling uncertainty is instead reserved for the other side of the ball, where it's unclear what we should expect. The Trojans have been an abject mess on defense in recent years, but the unit that struggled to stop anyone last season has been totally overhauled. Twelve of USC's 20 transfers and five of its seven freshmen come on the defensive side, many of whom are expected to have roles right away.

That turnover makes predicting USC's defensive prowess this season an inexact science. We have no idea how all of those new pieces will fit together in new coordinator Alex Grinch's scheme. Or whether those new pieces were a fit for the defense in the first place.

But on paper, there are reasons for optimism. For one, USC added a ton of talent where it was arguably weakest — at linebacker, starting with Lee, whose ascent as a locker room leader has been noteworthy. He's joined by Arizona State's Eric Gentry, a fellow freshman All-American, former Utah signee Carson Tabaracci and Auburn transfer Romello Height in a linebacker room that looks nothing like it did a year ago.

The same can be said of USC's secondary, which could see as many as four new starters.

"We expect to have a national championship-caliber defense here at USC," Riley said. "I believe we have the people to do that."

Who will be the Trojans' top pass rusher?

Former top recruit Korey Foreman was supposed to step right into the role of fearsome pass rusher as a true freshman. That lofty vision never quite crystallized. And after a disappointing debut season, it's hard to know what the future holds for Foreman.

For now, it doesn't appear that a starting role is a part of that picture. Foreman sat out part of the spring with an injury, allowing Height to surpass him on the depth chart and step seamlessly into the role of starting edge rusher.

Whether he'll hold on to the spot through training camp is unclear. But after hearing coaches and players rave about Height's performance in the spring, there's no reason to think he'll lose his grip on the role.

There's still plenty of time for Foreman to figure it out, of course. In the spring, he reiterated several times how "blessed" he was to have a fresh start on a rebuilt USC defense.

No one on that unit needed a fresh start more than Foreman, and arguably no one on USC's defensive front has more talent. Whether one will unlock the other this season is another question entirely.

How does Bobby Haskins' healthy return shake up the offensive line?

He was expected to be one of USC's most significant portal additions. But an ankle injury held new transfer lineman Bobby Haskins out of spring ball, delaying his debut and adding intrigue to a brewing battle on the offensive line.

Understand this: Haskins was not brought in as a grad transfer to ride the bench. Now that he's healthy, the expectation is he'll step in right away at left tackle, where he started 20 games for Virginia. The real question is whom he might displace in the process.

Courtland Ford and Jonah Monheim were USC's starting tackles for much of last season, and both will be in contention to start opposite of Haskins. If Ford wins the job, Monheim could possibly kick inside to right guard, where Justin Dedich started for most of the spring.

A redshirt senior, Dedich has dutifully waited his turn, playing the role of swing lineman for several seasons. Could his chance finally emerge in his fifth season at USC?

How much will USC's top freshmen be involved this fall?

With so many new players, their first-year counterparts haven't quite received the same billing ahead of fall as they usually do. But there are a few freshmen who could be household names by the end of camp.

The most obvious is Domani Jackson, the top prospect in the state for the 2022 class. USC's secondary is a wide-open competition, and Jackson has the chops to make an immediate impact. While Colorado transfer Mekhi Blackmon is sure to snag one corner spot, the other is up for grabs. It's rare to see a freshman step in right away at cornerback, but Jackson is in rarefied air as an athlete.

His Santa Ana Mater Dei High teammate, Raleek Brown, could make a similar splash on the other side of the ball. A true all-purpose threat capable of catching passes out of the backfield, Brown won't start in a traditional running back role as a freshman. Rather, he'll be deployed as a runner or receiver however Riley sees fit.

It may take a while for that role to crystalize. Once it does, Brown may very well be a fixture in the offense by season's end.

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