BATON ROUGE - Oh, Coach O!

One team.

One heartbeat.

And one big time upset.

In one of its biggest upset losses in school history, No. 22 LSU of the Southeastern Conference lost to 20-point underdog Troy of the Sun Belt, 24-21, in front of a mostly empty Tiger Stadium on homecoming Saturday night.

The loss joins the ranks of the infamous loss by LSU to Alabama-Birmingham, 13-10, on Sept. 23, 2000, in the first season of former coach Nick Saban, but the Tigers were not ranked for that game and had gone through eight losing seasons over the previous 11 years before that season. It was the most significant upset of LSU since the No. 8 Tigers were shocked by Miami of Ohio, 21-12, on Sept. 20, 1986.

For Troy, it was perhaps the biggest win in school history as a Football Championship Subdivision (FCS) school. The Trojans, a Division II power in the 1980s with national championships in 1984 and 1987, defeated No. 17 Missouri at Troy, 24-14, in their first year in the Sun Belt. This victory was over an obviously sliding program, but one that just played in a major bowl last season, finishing 8-4 after a 29-9 win over No. 13 Louisville in the Citrus Bowl, and played in the national championship game just over five years ago.

And Troy never trailed. The Trojans (4-1, 1-0 Sun Belt) led 17-0 early in the third quarter and by 24-7 midway through the fourth quarter, and held on.

"We were out-coached and out-played tonight," Orgeron said. "I've got to keep this team together. They're hurting in there. We've got to do some soul searching. It seems like we got out-physicalled by Troy tonight, which is not LSU football. I've got to do my best job right now."

LSU (3-2, 0-1 SEC) had drawn within 17-7 with four minutes to play in the third quarter on a 7-yard touchdown pass from true freshman quarterback Myles Brennan to tight end Foster Moreau and appeared ready to come back. LSU inside linebacker Devin White had just recovered a Troy fumble at the Troy 4-yard line to set up the touchdown.

LSU had just driven 67 yards in six plays before that, but wide receiver Derrick Dillon fumbled after catching a short pass from Brennan at the Troy 7-yard line.

Brennan started the third quarter for regular starter Danny Etling and completed 4 of 5 passes for 68 yards with the touchdown.

Brennan had LSU driving again early in the fourth quarter, but he threw his second interception in parts of two games. Etling had not thrown an interception this season until the final seconds when LSU was desperately driving for the tying field goal.

Troy took that Brennan interception and drove 64 yards in 10 plays and 6:30 for a 7-yard touchdown run by tailback Josh Anderson and 24-7 lead with 8:14 to play in the game.

Etling replaced Brennan on LSU's next possession and immediately put the Tigers in the end zone. He found wide receiver Russell Gage for a 34-yard touchdown pass with 7:41 to play in the game, cutting Troy's lead to 24-14. The drive covered 51 yards in three plays and took only 28 seconds.

Etling, who finished 17 of 25 for 198 yards and two touchdowns, drove LSU 92 yards in 13 plays on his next possession to get the Tigers within 24-21 with 1:59 left on a 20-yard touchdown pass to Moreau.

LSU tried an onside kick, but Troy recovered. The Tigers got the ball back with just 18 seconds left and did not mount a serious drive.

"Back to the drawing board," Orgeron said and proceeded to criticize first-year offensive coordinator Matt Canada and second-year defensive coordinator Dave Aranda. "I've taken the blame for the other games, but we've got to call better plays. And we've got to stop them on defense."

LSU was held to zero points and 158 yards in the first half and trailed the Trojans, 10-0, at the break. Then Troy scored a touchdown on the first possession of the third quarter to take a 17-0 lead with 13:06 to play in the period.

Troy put up 165 total yards and took a 7-0 lead in the opening minutes of the game as LSU tailback Nick Brossette fumbled on the first offensive play of the game. He had gained five yards, but safety Cedarius Rookard rocked him with a hit, and he fumbled. Safety Kris Weatherspoon recovered for the Trojans at the LSU 30-yard line just seven seconds into the game.

Orgeron did not like that play call to Brossette.

"Our third string back got the ball on the first play of the game," he said. "Darrel Williams should've got it. I was not aware that was how we were going to start the game. If I could have that call back, I would've given it to Darrel."

Williams led LSU with 69 yards rushing on 17 carries. Brossette never carried again.

LSU forced a third-and-four play from its 24 after the fumble by Brossette, but quarterback Brandon Silvers found wide receiver Emanuel Thompson for 16 yards to the Tigers' 1-yard line.

Troy wide receiver Emanuel Thompson (8) is stopped just shot of a touchdown by LSU linebacker Devin White (40) and linebacker Corey Thompson (23) in the first half of an NCAA college football game in Baton Rouge, La., Saturday, Sept. 30, 2017.

Silvers scored on a 1-yard run on the next play for a 7-0 lead with 13:13 to play in the opening period after Evan Legassey's extra point.

Legassey then hit a 37-yard field goal as time expired in the second quarter for the 10-0 lead. Both teams had left the field for halftime before the field goal as time had apparently ran out. But upon further review, the previous play had ended with the Troy player getting out of bounds to stop the clock with two seconds left. So, both teams rushed back onto the field. Two seconds were put back on the clock, and Legassey hit it.

The Tigers drove 62 yards in seven plays in the second quarter, but Jack Gonsoulin missed a 35-yard field goal with 2:32 to play in the half. Legassey previously missed a 36-yard field goal with 6:25 left in the second quarter, so LSU could have trailed 13-0 at the half.

Brossette, a junior from University High in Baton Rouge, started in place of injured tailback Derrius Guice, who has been bothered by a ankle/knee injury. Guice did dress out for the game but did not play in the first half. Brossette did not play again after the fumble.

LSU's defense could not stop Troy's running game. Tailback Jordan Chunn gained 191 yards on 30 carries. Silvers completed 16 of 28 passes for 157 yards.

Brennan finished 4 of 7 passing for 68 yards with an interception.

LSU trailed Troy by more eight years ago at halftime against Troy. The Trojans took a 24-3 lead over the defending national champions Nov. 15, 2008, and made that 31-3 early in the third quarter. LSU then stormed back for a 40-31 win.

That was not going to happen on this night.

"We've just got to get better," Orgeron said. "I've got to find out why we're not making plays."