Barkley is the polished, pedigreed Trojan -- a touted recruit since before his senior year of high school who is almost certain to enter the NFL draft this spring, when he is expected to be picked in the first round.
Osweiler? Only over the past two weeks has his play overshadowed his height, which you might have heard is 6-foot-8.
Osweiler is raw. Basketball was his No. 1 sport growing up. Barkley has been groomed most of his life to be an NFL quarterback. Former USC coach Pete Carroll repeatedly referred to him as an "outlier," Malcolm Gladwell's term for exceptional people, during Barkley's true freshman season.
But if this were a quarterback horserace, Osweiler would be gaining on Barkley. As nice as Barkley's numbers have been, and as impressive as he is throwing the football, he hasn't had many (any?) performances better than Osweiler's against Missouri in Week 2, when the Sun Devil completed 24 of 32 passes for 353 yards with three touchdowns and no interceptions and rushed five times for 34 yards and a score against a nationally ranked team. And that was Osweiler's third career start.
Said USC coach Lane Kiffin: "Big, powerful, strong arm. Really is doing a better job of moving to his second and third progressions in his reads than a year ago ... It's shocking to play this well. A big-time NFL talent."
Of course, Osweiler wasn't nearly as in control at Illinois the next week. He completed 25 of 45 passes for 256 yards with a touchdown and two interceptions. He again rushed for a score but also fumbled and was sacked six times. Coach Dennis Erickson didn't entirely blame his offensive line for that, either.
"We didn’t get rid of the football," Erickson said. "In our offense, you’ve got to get rid of the football. That’s just part of it. There were times when the ball should’ve been out and it wasn’t out, and we held it and got sacks."
Very few quarterbacks avoid bumps in the road in their development. Barkley certainly can identify during his two-plus years as a starter. During USC's meandering 20-9 record with him under center, he's been spectacular -- three games with five touchdown passes -- and inconsistent, see 27 career interceptions.
At present, Barkley ranks sixth and Osweiler seventh in the Pac-12 in passing efficiency. Will that order stay the same after the Sun Devils and Trojans tangle Saturday, with the No. 1 spot in the Pac-12 South Division on the line (USC isn't eligible for the postseason, so it can't play in the conference championship game)?
While many football players say stats don't matter -- only wins do, Barkley has made no secret that he keeps up with other quarterbacks.
"I definitely have them on the radar," Barkley said in April about other "name" Pac-12 quarterbacks, such as Stanford's Andrew Luck. "I'm aware of them. It is competition. Every quarterback wants to be the best at what they do. When I hear their name, I'm always trying to one-up them."
While Barkley didn't know who Osweiler was then, he probably does now. Osweiler, however, said he doesn't compete with the other Pac-12 quarterbacks. Or he sorta said that.
"Obviously, I know what other quarterbacks are doing around the conference," he said.
The primary focus is inside the locker room. The Sun Devils took the loss at Illinois hard, as they should have since they lost a game they should have won. Nine possessions inside Illinois' territory netted just two touchdowns. They had three turnovers, missed a chip shot field goal, gave up six sacks and had eight penalties in a 17-14 defeat in which they outgained the Illini 362 yards to 240.
"Guys were pretty hurt," Osweiler said. "It was pretty gut wrenching for me. But the positive thing is as hurt and as down as everyone was in the locker room after the game, by the time we hit the buses to go to the airport everyone was like, 'Hey, this one is behind us. We've got USC this week. We're at home. Let's go have a great week of practice.' It was pretty cool to see guys bounce back so quickly."
When asked if some fans might say, "same, old Sun Devils," he added: "A lot of people are looking at this loss like it's the end of the world. It's just one loss early in the season. It's a nonconference game. It's a great learning tool for us."
Learning is about experience, and that's what Osweiler lacks compared to Barkley.
"I don't care how athletic you are or how good you are, experience makes you better," Erickson said. "He'll learn from what happened."
That means getting rid of the football faster against a Trojans defensive line that is more talented than Illinois'.
The Sun Devils seemingly have more to play for. A win over the Trojans would put them in good position in the Pac-12 South, seeing that Utah already lost at USC. It might push them back into the national rankings. It certainly would energize a fan base hungry for success. It would get the critics off Erickson's back.
Oh, and it would end an 11-game losing streak in the series. And yes, that span of futility has come up this week.
"Obviously that talk is going around the building, reminding us how long it has been," Osweiler said.
Ending that streak may come down to Osweiler, the surging new guy, outplaying Barkley, the established star.