South Alabama did it again.

Sophomore quarterback Cole Garvin, making his first career collegiate start, threw three touchdown passes and the Jaguars made big plays on defense and special teams in the fourth quarter of a 42-24 upset of No. 19 San Diego State on Saturday at Ladd-Peebles Stadium in Mobile, Ala.

South Alabama opened the season by beating Mississippi State. On Saturday, they ended the Aztecs' 13-game winning streak by capitalizing on a pair of San Diego State miscues in the fourth quarter.

Garvin hooked up with Josh Magee in the corner of the end zone on a 20-yard touchdown pass that gave the Jaguars a 28-24 lead early in the fourth quarter. They extended the lead minutes later, taking advantage of a bad snap on a San Diego State punt that set up Dami Ayoola's short touchdown run.

Coach Joey Jones' team then salted the game away on Devon Earl's 75-yard fumble return that put the Jaguars in command, leading 42-24 with four minutes to play.

"The Mississippi State game was huge," Jones said, trying to put Saturday's win in perspective. “San Diego State has been dominating people and they were No. 19 in the country. It's the next game and I'm excited about our program and what we've been able to do this season, beating an SEC West team and a top 20 team. Those two things are huge for our program, but those are just one more game in reaching the goals we want to accomplish. Our guys don't want to settle for mediocre right now and they want to be the very best."

Donnell Pumphrey, the nation's leading rusher, finished with 151 yards and a touchdown for the Aztecs, who suffered their first loss since Sept. 26, 2015, against Penn State. Pumphrey topped 5,000 rushing yards for his career and became the Mountain West's career rushing leader.

"I think we still had a chance to win until we snapped the ball over our punter's head,” San Diego State coach Rocky Long said. "Then we fumble and they return it for a touchdown and the game is over. I think the game could have gone down to the wire with a chance to win it if we don’t do that."

Garvin completed 16 of 21 passes for 242 yards with three touchdowns and one interception.

"We had a great week of practice," Garvin said. "I was nervous until I got on the field. I mean, I haven't played in three years. But we had a great game plan and my receivers made some great, great catches."

Garvin, a Marshall transfer, sat out last season. He got the start in place of injured starting quarterback Dallas Davis. The Jaguars also were missing injured starting running back Xavier Johnson but made the most of what they had in the program’s first win over a ranked team.

A 34-yard field goal by San Diego State kicker John Baron II with five seconds left in the second quarter gave the Aztecs a 16-14 lead after a back-and-forth first half. Rashaad Penny and Pumphrey had touchdown runs in the first half for San Diego State.

South Alabama running back Tyreis Thomas opened the scoring with a 12-yard touchdown run that gave the Jaguars an early 7-0 lead. It was the first time the Aztecs had trailed this season.

Garvin, making his first career collegiate start, threw a 37-yard touchdown pass to Kevin Kutchera on a flea-flicker that put the Jaguars ahead 14-6 at the end of the first quarter. Garvin had a chance to extend the lead late in the first half but was intercepted in the end zone by San Diego State's Derek Babiash.

San Diego State quarterback Christian Chapman completed 13 of 22 passes for 159 yards, with a touchdown pass to tight end Kahale Warring that had the Aztecs in front 24-21 heading into the fourth quarter. But San Diego State didn't score again and was doomed by the mishandled punt snap that set up South Alabama inside the Aztecs' 10-yard line and a botched handoff that Earl took to the house to seal the upset for the Jaguars, who were nearly three-touchdown underdogs.

"I'm not happy with how anyone played," Long said. "That goes right back to me and the coaching staff. If we have decent players and they don’t play well, that's coaching."

NOTES: San Diego State entered the game on a 13-game win streak, second longest in the nation behind Alabama (16). It's also the Aztecs' longest win streak since legendary coach Don Coryell led the program to 21 straight wins from 1968 to 1970. ... San Diego State was ranked 19th in the Associated Poll this week, their highest ranking since 1977. ... Saturday's game was South Alabama's first at home against a ranked team. ... This is the second meeting between San Diego State and South Alabama. The Jaguars beat the Aztecs 34-27 in overtime last season. … South Alabama had four sacks.