STARKVILLE, Miss. -- South Alabama pulled off the first major upset of the college football season, holding off Mississippi State 21-20 Saturday when Westin Graves' 28-yard field goal try smacked off the upright in the final seconds.

A four-touchdown underdog, the Jaguars took down an SEC team for the first time in school history.

"I'm part of the South Alabama Jaguars," beaming linebacker Roman Buchanan said, "that beat Mississippi State."

Down 17-0 at halftime and still trailing 20-7 in the fourth quarter, South Alabama rallied to take the lead on Dallas Davis' 4-yard TD pass to Gerald Everett with 57 seconds left.

Mississippi State immediately drove down the field and got in position for a field goal. But Graves' kick hit the left post and fell harmlessly to the turf at a stunned Davis Wade Stadium.

Most of the Mississippi State fans had long gone home on a hot afternoon and all that was left was a screaming contingent of a few hundred South Alabama fans.

South Alabama coach Joey Jones said he was proud to give the Sun Belt Conference a high-profile non-conference victory.

"To win a ballgame like this is a blessing," Jones said.

Two days after Appalachian State almost toppled No. 9 Tennessee before losing in overtime, South Alabama kicked off a season that follows a year full of wild endings.

Davis -- a sophomore who was making his first career start -- threw for 285 yards and two touchdowns. He said the Jaguars' rally in the second half wasn't due to any major changes.

"It was just coming out and playing better," Davis said. "Ever since the beginning of camp, coach has preached playing fast and finishing strong. We didn't start as fast as we wanted, but we dang sure finished strong."

Damian Williams finished with 143 yards passing and 93 yards rushing, including several impressive plays on the final drive for the Bulldogs.

MISSISSIPPI STATE'S QB SITUATION

Mississippi State came into preseason camp with a four-man quarterback race that was whittled to three in mid-August when Elijah Staley transferred. The Bulldogs started Nick Fitzgerald, but after two ineffective drives replaced him with Williams, who gave the offense some spark on the way to a 14-0 lead. Williams, however, wasn't as effective in the second half until the final drive that ended with the missed field goal.

THE TAKEAWAY

South Alabama: It's a massive win for the Jaguars, who lost badly to Mississippi State in both 2012 and 2014. The Jaguars were 0-4 against SEC opponents.

UP NEXT

South Alabama: The Jaguars host Georgia Southern next Saturday in their first Sun Belt game of the season.

Mississippi State: The Bulldogs host South Carolina next Saturday in their first SEC game of the season.

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Follow David Brandt on Twitter: www.twitter.com/davidbrandtAP . AP College Football website: www.collegefootball.ap.org .