It started out looking like USC and its fans would be able to leave the Coliseum on Saturday night feeling upbeat about the homecoming game against Arizona -- for that matter, upbeat for the first time in a while after a home game.

The Trojans built a big early lead, piled up rushing yards with ease, invigorated the few fans in attendance by giving freshman quarterback Jaxson Dart significant action, and while the defense wasn't great, it at least tallied 5 sacks.

Instead, the Trojans managed to make things tense in the fourth quarter before closing out an ultimate 41-34 win over a team that has now lost 20-straight games.

Worse, USC's best player, heart-and-soul of the team and Biletnikoff Award candidate Drake London crumbled to the turf with a serious-looking ankle injury after scoring his second touchdown of the game late in the first half.

London was carted off the field, pulling his jersey over his face in what was just about the worst sight Trojans fans could have imagined coming into the day.

"That was horrible. He's on pace to have probably one of the best statistical seasons in college football history if I would guess, and to see him go down was awful and I feel terrible for him," offensive coordinator Graham Harrell said.

"It sucks. The best receiver, the best player on the team, so it hurts a lot," quarterback Kedon Slovis said.

Interim head coach Donte Williams didn't know the severity of London's injury after the game as more tests were pending, but he acknowledged there's "a fear" that it could be season-ending -- especially with only four regular-season games left.

RELATED: Coaches, teammates react to Drake London injury | Jaxson Dart, Kedon Slovis react to USC's QB rotation | WATCH: Postgame video interviews

That cast a pall over everything else, as it's possible the one consistent positive of this lost season has now played his last game as a Trojan.

It happened on a routine-looking 6-yard TD pass from Dart that put USC up 28-7 late in that second quarter, when the vibes were all positive, but Arizona cornerback Christian Roland-Wallace inadvertently came down on the back of London's right leg as their momentum brought them to the turf.

London, who leads all Power 5 receivers with 88 catches and 1,091 yards, already had 9 catches for 81 yards and 2 TDs by that point and was on his way to yet another monstrous stat line.

Instead, he was placed on cart and put in an air cast, as his teammates gathered around him before he was taken to the locker room. (Roland-Wallace came over to talk to London as well.)

Whether it was directly related or not, the Trojans (4-4, 3-3 Pac-12) just didn't look the same the rest of the game as winless Arizona (0-8, 0-5) would make it a one-score game late in the fourth quarter.

Asked afterward if it was a satisfying win, at least a couple Trojans said no.

"No, definitely not," defensive end Drake Jackson said. "We could have definitely came out and did much better than what we did, so we've just got to come tomorrow and watch film and see what we did wrong."

Said right tackle Jalen McKenzie: "A win is a win, but the Pac-12 South is in limbo right now and all of our hopes are still right there. We're trying to go to a conference championship so we need to play better than that win. ... A win is a win, but we'd like to win better than that. That's not acceptable for our standard of winning."

It was the same familiar themes for this USC team, which racked up 9 penalties for 100 yards -- including some very costly ones that contributed to the second-half offensive swoon.

Early in the third quarter, running back Keaontay Ingram -- who was the star of the game with 204 rushing yards and a TD on 27 carries -- broke off what looked to be a 66-yard touchdown run. But a holding penalty on wide receiver Tahj Washington wiped out the final 38 yards and the Trojans eventually settled for a 23-yard Alex Stadthaus field goal.

In the fourth quarter, Ingram reeled off a 46-yard run down to the Arizona 17-yard line, but an unnecessary roughness penalty on right guard Liam Jimmons negated the final 28 yards of that gain and the Trojans would ultimately punt.

"I think we kind of got happy and got complacent a little bit. We've got to finish better," Harrell said. "... That second half we got a little conservative because we had a lead and wanted to run the football, did that, and really if you take the two penalties away on Keaontay's [runs] you probably score a lot of points in the second half too."

Instead, after going into halftime up 35-14, everything started to unravel.

Not only did the offense go flat, but Arizona linebacker Anthony Pandy intercepted Slovis and returned it 37 yards for a touchdown early in that third quarter, and the USC defense later allowed Wildcats QB Will Plummer to scramble for a 16-yard touchdown on a long third-and-goal to make it 38-28 early in the fourth quarter.

Kicker Tyler Loop cut it to 38-31 with a 25-yard field goal with 6:04 to play, on a drive that was aided by a pass interference penalty on cornerback Jayden Williams.

The second-half struggles wouldn't cost USC the game, but along with London's unfortunate injury, they did negate many of the positive feelings that were generated in the first half.

The exceptions being the play of Ingram and the general success of the QBs.

On the next play after Arizona had made it a 7-point game, Ingram rumbled for a 45-yard gain and Stadthaus connected on a 40-yard field goal with 3:19 remaining to sap some of the Wildcats' momentum.

Arizona got a late field goal but USC was able to run out the final 1:25, with Ingram plowing through the line for the final first down.

Ingram averaged an impressive 7.6 yards per attempt on his season-high 27 carries, and he's now rushed for at least 124 yards in three of the last four games.

"Running back is just a feel, just getting in a rhythm -- not only me but with my offensive line as well," said Ingram, who has also totaled 51 carries the last two games while seeing his role significantly increase. "When my number's called I've just got to go execute, and one thing that we believe in, Coach Donte preach[es] all the time, be physical and bring that physicality. And I feel we did that."

Said McKenzie: "He could have had like 300 without penalties -- can't leave stuff like that on the field. That's all of our fault."

As for the quarterbacks, Slovis finished 15 of 21 passing for 204 yards, 2 TDs and 1 INT. He led touchdown drives on USC's first two possessions, including a 62-yard bomb to Gary Bryant Jr., and later dropped a perfect dime to Bryant for a 15-yard touchdown at the end of the first half.

Dart went 12 of 18 for 109 yards, 2 TDs and 0 INTs, tossing both of his scores to London on his first two series of action, including leading a 15-play, 96-yard drive in 4:32. He came back in for the first two series of the fourth quarter as well.

"Both of them had good days. Both of them [were] efficient. ... Both of them passed the ball, both of them scored touchdowns, the offense moved with both of them in the huddle. Both of them made little small mistakes that they'll continue to clean up. We was efficient with both. At the end of the day we put up 41 points," Williams said.

Meanwhile, Bryant finished with 3 catches for 89 yards and 2 TDs, Washington had 8 receptions for 87 yards and Tuli Tuipulotu led the defense with 2 sacks.

"They won the second half of the football game, but I do like the way that we won the line of scrimmage tonight -- even on defense we stopped the run, but [offensively] we ran the ball. That was a great feeling to get back to 'SC ways as far as the way we run the ball and stop the run," Williams said. "But it was still way too many mistakes. I look at this and I see 9 penalties for 100 yards. That's unacceptable."

Against an opponent that has lost 20 straight games, lost to a middling FCS team and got blown out 34-0 by a bad Colorado team.

As McKenzie said, a win is a win, and this team sure needed a win -- especially in the Coliseum after being blown out in its last three home games -- but ultimately this was not a win that is going to make anyone feel any differently about the direction of this season.

Especially in light of the London injury.