There was something driving him besides the need to see if he could get out of bed.

DeShaun Foster had spent the previous afternoon at UCLA Medical Center, his viral symptoms forcing the star freshman into isolation at the team hotel in Pasadena the night before the 1998 cross-town rivalry football game.

Some chicken soup and about five hours of sleep did wonders for his sore throat. Maybe the best high school running back to ever come out of Orange County woke up ready to devour the college that had only wanted him if he would play defensive back.

“After having the type of season that I had my senior year and then being told that I’m not good enough to play running back at this school,” Foster told The Times this week, referring to USC without mentioning it by name, “that’s going to motivate you.”

Tustin High tailback DeShaun Foster runs past Foothill’s Eric Davidson (72) Dana Pino-Dempsey (2) and Joshua Harvey (20).

(Al Schaben / Los Angeles Times)

Well, yeah. If an infection and a low-grade fever couldn’t stop him, then Chris Claiborne and Rashard Cook had no chance.

The stakes couldn’t have been higher for the third-ranked Bruins. A victory over USC at the Rose Bowl would give UCLA a record eighth consecutive triumph in the rivalry while extending its school-record winning streak to 20. More important, it would keep the Bruins, ranked second in the Bowl Championship Series standings behind Tennessee, in the running to play in the first BCS championship game in the Fiesta Bowl.

More than a quarter of a century later, Foster will step onto that same field Saturday night needing to prove himself anew against another team wearing the loathsome cardinal and gold.

Now the rookie head coach at his alma mater, the 44-year-old is a lot like his 18-year-old self. He’s trying to show he belongs after making the unconventional move from position coach to head coach. His team’s bowl fortunes hang in the balance. And, of course, he wants to pound that other L.A. school into the perfectly manicured field at his home stadium.

“I’ve been in it a long time,” Foster said of the rivalry, “so I understand the importance of it.”

Having drawn comparisons to former Rams running back Eric Dickerson because of an upright rushing style in which he bowled over defenders, not to mention records, Foster sparked a massive recruiting war while at Tustin High.

Michigan, Ohio State, Colorado, Texas, Nebraska, Washington, USC, UCLA, Oregon, Wisconsin and Arizona State all wanted him. USC was among the schools that made a fatal mistake in their pitch: They told the high school senior they wanted him as a defensive back, taking them out of the running.

Myron Miller, then Foster’s coach at Tustin, said he understood the thinking. Foster enjoyed nearly as much success at linebacker and safety for the Tillers as he did at running back, where he piled up an Orange County-record 3,398 yards and a Southern Section-record 59 touchdowns in his final high school season.

“He was good on that side of the ball,” Miller told The Times this summer, “and I told him years later because of the way they hammer running backs that I thought he’d still be playing if he played safety because he would be giving the hits instead of taking them.”

Bobby Field, the UCLA defensive backs coach who also oversaw the team’s recruiting efforts in Orange County, was selfishly thinking the same thing. He was also smart enough to understand what Foster wanted.

“I did mention to him defensive back because I was coaching them and I would have loved to have coached him as a safety,” Field said, “but in my heart I knew in his heart he was a running back.”

On signing day, Foster remained torn between finalists Texas and UCLA as he headed to Tustin. By the end of first period, he had made up his mind, swayed by another running back who did big things for the Bruins.

Tustin High School’s DeShaun Foster (26) gets jumps as Brea Olinda tries to tackle him by his shoestring during a very wet game. Tustin won 9-7.

(Kevin P. Casey/Los Angeles Times)

“Skip Hicks had just led the nation in touchdowns,” Foster said, “and I just remember coming to games [thinking] like I know I can do that, I can get out there and do that exact same thing, so that was a big factor in just the fact that they would keep me at running back.

“A lot of people wanted to play me on defense and they might have been telling me, ‘Yeah, you can come play running back’ and get me and then move me to defense. I just knew that I would at least get a shot being a local player at this school.”

Nine months later, there was more to avenge in Foster’s first rivalry game than his spurning by a local school.

He was also seeking his first victory in another rivalry.

While in high school, Foster and Tustin had gone up against Carson Palmer and Santa Margarita three times. The USC-bound Palmer had prevailed on every occasion, including a 55-42 victory in a divisional high school championship game that was widely considered the best in Orange County history.

Foster rushed for 378 yards and scored on runs of 25, 25, 31, 10, 14 and one yard. His third touchdown gave the Tillers a 20-14 lead.

Tustin High’s DeShaun Foster (26) scores a touchdown as Valencia High’s E.J.Smith (9) tries to tackle him on Nov. 20, 1997.

(Los Angeles Times)

“He was a Mack truck,” said former UCLA offensive tackle Kris Farris, a Santa Margarita graduate watching his old high school team face his future Bruins teammate.

He was also forced to log even more mileage than usual. A safety who usually subbed for Foster to give him occasional breathers had gotten hurt the week before, forcing him to play the entire game.

Worn down by all that running, Foster pulled up with cramps on what should have been a long touchdown run. The Tillers also dropped a pass that would have put them up by two touchdowns.

It was too much to overcome against a deeper opponent. Palmer passed for 413 yards and five touchdowns to go with one compliment during a postgame embrace.

“You were awesome,” Palmer told Foster. “You’re the man.”

More than two decades later, Foster chuckled while pondering what might have been had he not been forced to play both ways.

“It probably wouldn’t have been fair,” Foster said, “if I could have just been fresh.”

On the morning he would face USC for the first time, still trying to shake off his symptoms, Foster received a pep talk from his coach.

Bob Toledo told him that he was destined to join the list of players who had great games while sick. Didn’t he remember Michael Jordan’s flu game from the previous spring, when the Chicago Bulls superstar scored 38 points in the NBA Finals?

Well, yeah, but Foster wasn’t even UCLA’s starting tailback — that was Jermaine Lewis.

Then again, it didn’t take long on that afternoon for Foster to become the featured part of the Bruins offense.

He displayed a nice burst on his first carry, gaining 15 yards. Showing his versatility, he caught a four-yard touchdown pass from quarterback Cade McNown to put UCLA ahead, 7-3.

Later in the first quarter, on fourth and goal from the one, he plunged over the goal line for a touchdown to put UCLA up 14-3.

Wasn’t he supposed to be sick?

Foster finally felt his chest burning toward the end of a 65-yard touchdown run in which he was in the open field once he got past cornerback Daylon McCutcheon. By halftime, Foster had rolled up 107 rushing yards.

His fourth touchdown came early in the fourth quarter on another one-yard plunge. He had set a school record for touchdowns by a true freshman and would have broken it had he not had the ball ripped out of his arm for a fumble while trying to score from the one-yard line late in the game.

Near the end of UCLA’s 34-17 rout, ABC broadcasters Gary Danielson and Brad Nessler, nicknamed it “Foster’s freeze” in honor of the freshman putting USC’s upset bid on ice. Palmer struggled that day for the Trojans, his 252 passing yards and two touchdowns offset by two interceptions, a fumble, six sacks and a run game that generated only 3.9 yards per carry.

The Trojans didn’t want Foster at running back? Well, it was their loss.

“I was the best back in the area, and they told me I could play defense,” Foster said all these years later. “So, four touchdowns and [109] yards later, I think the point was taken who was the best running back.”

Two weeks after the big rivalry triumph, UCLA’s hopes of playing in the first BCS title game crumbled during a 49-45 loss to Miami in the dreaded “Hurricane Bowl.” The Bruins went on to lose to Wisconsin in perhaps the first Rose Bowl seen as a consolation prize.

Foster said he eventually got over the snub by his rival.

He never beat USC again as a player, finishing 1-2 before heading to the NFL.

Returning to his alma mater in 2012 as a volunteer assistant under coach Jim Mora, Foster was part of three consecutive victories over the Trojans. He later recruited Josh Kelley, who ran for a rivalry-record 289 yards during the Bruins’ 34-27 victory at the Rose Bowl in 2018.

UCLA running back Joshua Kelley (27) pushes off USC cornerback Ajene Harris (27) during the Bruins’ win over the Trojans at Rose Bowl on Nov. 17, 2018.

(Getty Images)

UCLA has not beaten USC on its home field since, making the game between the Bruins (4-6 overall, 3-5 Big Ten) and Trojans (5-5, 3-5) on Saturday another opportunity for redemption.

Unusually jaunty when he met with reporters Monday, Foster poked fun at the academic merits of the school across town.

“A lot of families,” Foster said, “the smarter one usually comes over here and the other one goes to the other school and then the family’s torn, you know what I mean?”

Foster said he wouldn’t show his players footage of his highlights from the 1998 game, but there’s probably no need given his demeanor.

“You can feel that passion for this game,” linebacker Carson Schwesinger said.

UCLA coach DeShaun Foster leads the Bruins onto the field before a game against Oregon at the Rose Bowl on Sept. 28.

(Marcio Jose Sanchez / Associated Press)

Beating USC would make Foster’s first season an unqualified success and significantly boost his efforts to bring in the name, image and likeness dollars needed to upgrade the talent on his roster.

Asked about the significance of a victory over USC, Foster said it wouldn’t be about validating him.

“We’re going to be a success regardless,” Foster said. “I mean, people on the outside are going to judge me on how my record is, but as long as these boys are playing hard for me every game and you can see that, that’s all I want at the end of the day.

“This is more for the seniors, like, seriously. I truly want to send them off the right way, with a victory against this team, and then finish out the season and make sure that we’re bowl-eligible so that they can go out on the right note.”

Doubted once more, his team favored to lose in every betting line, there’s nowhere Foster would rather be.