PASADENA, Calif. (AP) Kedon Slovis and No. 16 Southern California continue to be kings of the fourth-quarter comeback.

Slovis completed his third game-winning drive of the season, finding Amon-Ra St. Brown for an 8-yard touchdown pass with 16 seconds left to lift the Trojans over UCLA 43-38 on Saturday night after trailing by 18 in the third quarter.

UCLA took a 38-36 lead with 52 seconds remaining on Nicholas Barr-Mira's 43-yard field goal, but USC coach Clay Helton said he wasn't fazed considering what he saw his team do earlier in the season.

''I knew if we just had one more opportunity that they would make something happen. That's just who this team is,'' he said. ''I've always felt great quarterbacks shine when the game is on the line, and I've watched No. 9 in three situations just do what championship quarterbacks do. And he's done it against this league now his whole career.''

Gary Bryant returned the kickoff 63 yards to the Bruins 43, and Slovis connected with Tyler Vaughns on a 35-yard reception despite great coverage by UCLA's Mo Osling III. St. Brown the caught his second TD of the game on the next play.

''I overthrew Tyler earlier in the game, so I just wanted to give him a chance to make a spectacular catch,'' said Slovis, who is the first USC quarterback since Sam Darnold to have five passing TDs in two straight games. ''Then, on the goal line, we saw man again. We had a run called but I checked it over to Amon-Ra, and that worked out for us. Probably gave coach Helton a bit of a tough time, but it worked out for us.''

The Trojans clinched the Pac-12 South title earlier in the day when Utah beat Colorado.

The victory over UCLA completes a trifecta of comebacks for the Trojans (5-0). They trailed by 13 in the Nov. 7 opener to Arizona State before Slovis threw two TD passes in the final 3 minutes for a 28-27 victory. USC then won 34-30 the following week at Arizona on Vavae Malepeai's TD run with 25 seconds to play.

''At this point we've been through that situation so many times that I feel like everyone kind of has their cool and has that experience from those other games, it really helps,'' said Slovis, who completed 30 of 47 passes for 344 yards and two interceptions. ''This is probably the most difficult situation we've had time-wise but none of the guys seemed fazed, and that definitely helps when you're in that pressure situation.''

St. Brown and Drake London each had two touchdown receptions, Vaughns caught eight passes for 110 yards and Malepeai ran for 110 yards in the 90th Crosstown Showdown.

USC trailed 28-10 early in the third quarter before scoring touchdowns on five of its seven second-half drives. USC was still down 35-23 at the start of the fourth quarter before Malapei's 10-yard run, and London scored his second TD on a 9-yard reception. USC went for two after London's score but couldn't convert.

USC was able to rally due to UCLA mistakes. The Bruins (3-3) twice turned it over on downs, fumbled on a fake punt and Dorian Thompson-Robinson was picked off.

''Slovis is one of the top QBs in the nation, so they were going to adjust,'' UCLA coach Chip Kelly said. ''It was kind of like a heavyweight fight where both sides were hitting blows. We had a shot at the end but didn't convert.''

Thompson-Robinson was 30 of 36 for 364 yards with four touchdowns and two interceptions. Demetric Felton rushed for 90 yards and had two TDs receiving, and Craig Dulcich had eight receptions for 167 yards, including a 69-yard touchdown in the third quarter for UCLA's longest play of the season.

''This isn't a normal game or a normal loss. This one hurts,'' Thompson-Robinson said.

STREAKING

Talanoa Hufanga intercepted a pass for the fourth straight game during the fourth quarter, which led to London's second touchdown. He is the first USC player since Sammy Knight in 1996 to pick off a pass in four straight games.

RARE SCORE

Fernea, a redshirt senior, scored only the second touchdown of his career on a quick screen pass that went for 33 yards.

The Bruins lined up trips left and Fernea got great blocks from Dulcich and Logan Loya to go untouched. It was only his second reception of the season and eighth of his career.

PLAY OF THE GAME

London put the Trojans on the board with one of the best individual effort plays of the season. On second-and-14 from the USC 35, Slovis stepped up in the pocket and found London downfield.

The sophomore caught it at the UCLA 33 and then shed six tackles en route to the end zone, including four attempts at trying to take him down in the final 10 yards to bring USC within 14-7 midway through the second quarter.

''Drake's a special player, and that play, gosh almighty, it gave me a heart attack when the ball went up in the air and then he caught it. Just looked like a damn horse carrying people into the end zone,'' Helton said. ''But, yeah, it really got the emotion out, allowed us just to relax for a second and take a deep breath.''

THE TAKEAWAY

USC: The Trojans had a tough game but should go up a couple spots in the rankings. It will have another short week to prepare for a game, but this one will be for the conference title.

UCLA: When the Bruins play clean football, they are usually able to win, but they had too many mistakes in the second half. In three years under Kelly, they are plus-15 in turnover margin and minus-26 in losses.

UP NEXT

USC: Will host Pac-12 championship game on Friday vs. Washington.

UCLA: TBA

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