It became clear through spring practice and fall camp that freshman Calen Bullock was ahead of the pack of USC's young safeties and that he could possibly contribute early on this season.

It's just that nobody expected that to be in a starting role in the very first game, as Bullock became the first true freshman safety to start a USC season opener since Su'a Cravens in 2013.

And it took less than a full quarter Saturday for the fans in the Coliseum to appreciate what those who have had access to practices since April have been seeing on a regular basis -- that Bullock seems to have advanced instincts and penchant for being around the ball.

With San Jose State facing a third-and-2 and approaching midfield with just under 5 minutes to play in that opening quarter, the Spartans went with what should be a high-percentage play as quarterback Nick Starkel dumped it off to running back Tyler Nevens out to the right. Nevens is a bowling ball of a rusher who often shakes off or pushes through tacklers, but Bullock read the play instantly, closing 7 yards in a snap while hitting Nevens just below the waist and wrapping up his legs so he couldn't spin out of the tackle.

It took a replay reversal to get the call right, but indeed Bullock had stopped the Spartans short, forcing a punt with that missile-like tackle that couldn't have come a split second later to achieve that result.

"I read the play, we watched it on film and every time on third-and-2 it seems like most times they try to get the ball to the back and I cheated and I made a great play," Bullock said.

Bullock, who got the surprise start with redshirt senior captain Isaiah Pola-Mao missing the game due to COVID, went on to lead USC with 8 tackles in the Trojans' impressive defensive performance in that 30-7 win.

Bullock's veteran teammates delighted in reflecting on his performance after the game, as they too have been impressed with his early emergence.

"We call him 'Sticks' because he's a tall, skinny kid. But that dude can cover ground," junior cornerback Chris Steele said. "There was a few plays where I would tell him, I'm really big on calling plays out, so I would tell him, 'Hey, play the post.' Sure enough that dude's right there breaking on the post making plays on the ball. So just seeing his growth is really just amazing to me. He was a dude that came in, enrolled early in the spring, bought into the program and now he's making plays on the biggest stage. I'm really looking forward to his development. He'll get more comfortable as the season moves along too."

Bullock made another nice play on third down in the second quarter on a third-and-8 play from the Trojans' 14-yard line. Starkel completed a short pass to Isaiah Hamilton across the middle designed for the receiver to pick up yards after the catch, but that wasn't possible with Bullock draped on him in tight coverage and delivering an immediate tackle. San Jose State would then miss the ensuing field goal.

"I thought he played a wonderful game, tackled extremely well especially on third down, was called into some man-to-man situations where he had to get runners and receivers on the ground and did that extremely well," USC coach Clay Helton said. "... We expect to see more of him both on defense and special teams, but he definitely showed us something in this game. Very impressive for a young person."

Especially one who didn't know he'd be playing such a prominent role until the middle of the week.

Bullock said he was told at some point Wednesday that Pola-Mao had tested positive for COVID and would be forced to miss the game.

"Really, it was no pressure. Coach told me I was starting on Wednesday because Isaiah got COVID. But really we preach the next man up so everybody's got to know what they're doing and there was no pressure on me," Bullock said. "... At first I was happy, my emotions was everywhere, I was calling my mom, really happy, and then I reached out to Isaiah really just telling him I got him, like I won't let him down."

Indeed, he followed through on that.

That doesn't mean Bullock wasn't facing some nerves early while making his college debut.

He said he tried to get out on the field in pregame and find a space off by himself to let the moment and the setting sink in and calm his emotions down.

By pregame warmups, though, he was bouncing around in drills with safeties coach Craig Naivar, dancing to the music in the stadium and looking primed for his opportunity.

"Coming into the game I was nervous. Of course, any freshman would be, and then once I got my first tackle it was football after that. I did what I had to do," he said.

Even though redshirt-freshman Xavion Alford was listed as the backup to Pola-Mao at free safety on the official depth chart, with Bullock slotted as the second-team nickel, the true freshman had played several positions in the spring and preseason and had the most trust of the coaching staff.

Pola-Mao and the Trojans' other older players made sure he was ready over the final days of preparation leading up to the game.

"He told me, 'You're made for this,' basically. We were preparing for this since spring and now I got the opportunity and it was my time, he said," Bullock recalled. "... Really the older guys, they prepare the younger guys really good, always on us, making sure we know our calls, and Coach Naivar making sure everybody know what they're doing. Like I said, we preach next man up."

Helton praised Bullock for arriving at USC last winter "with a sense of urgency to contribute early." Like Steele noted, Bullock came in as a long and wiry four-star prospect out of Muir High School in Pasadena, but Helton said he's put on 20 pounds of muscle since then (he's now listed at 6-foot-3, 180 pounds).

He was an effective two-way player in high school who was ranked the No. 8 safety and No. 130 overall national prospect -- part of USC's vaunted 2021 safety class that included four four-star signees from local high schools.

In Bullock's case, getting to play such a prominent role in his first game in the Coliseum was "just a dream come true," he said.

"Of course, my hometown's Pasadena, it's the Rose Bowl, but USC has always been my dream to play in the Coliseum and now I got the chance to do it and I took all advantage of it," he said.

What becomes of his role moving forward is hard to say. Helton said Pola-Mao could be able to rejoin the team later this week and starting nickel Greg Johnson made the play of the game with a 37-yard interception return for touchdown, so he is probably entrenched at that spot. The one to watch is the other safety position, where redshirt junior and new starter Chase Williams had some struggles Saturday.

Cornerbacks coach Donte Williams, who helped recruit Bullock to USC, reminded reporters after the game that the freshman is still developing and learning.

"I think he would say the same -- he played well but there's still some things he has to clean up communication-wise and things like that. But Coach Naivar and everybody else has done a great job with Calen," he said. "Calen, he's on his way, but he still has a long ways to go."

However it plays out, the Trojans now know what Bullock can do in a game setting, and it seems likely he finds his way into more opportunities this year.