HOOVER, Ala. — LSU had a bullpen filled with back-end arms. It started a pitcher sometimes used for midweek games. It faced the Southeastern Conference freshman of the year — and yet, somehow, the Tigers held a 10-run lead on Mississippi State in the fourth inning.

Despite everything that suggested LSU should lose on Friday night, baseball is not a predictable sport.

The Tigers won their elimination game 12-2 at Hoover Metropolitan Stadium, mercy-ruling Mississippi State by the seventh inning. They moved on to play top-seed Vanderbilt in the semifinals.

"This is exactly the way we drew it up and expected it to happen," coach Paul Mainieri said sarcastically. "You had to love our matchup there, right?"

The Tigers had pushed themselves through three exhausting days at the SEC tournament, advancing to a rematch with the Bulldogs, the team LSU had lost to 6-5 in 17 innings two days earlier.

Through two innings, LSU had struck out four times against freshman pitcher JT Ginn, a first-round pick in last year's MLB draft. At that point, Mainieri and shortstop Josh Smith spoke in the dugout. They thought Ginn would strike out 18 batters.

The Tigers didn't reach base until senior Chris Reid singled to lead off the third inning. He scored on a one-out double by second baseman Brandt Broussard.

"Everything started clicking," catcher Saul Garza said.

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Smith singled. Giovanni DiGiacomo walked. Antoine Duplantis singled, and relievers began throwing in the Mississippi State bullpen. LSU had jumped on Ginn.

The inning continued as Drew Bianco — a late addition to the lineup when LSU scratched first baseman Cade Beloso because of a sore wrist — grounded into a surefire double play, but Mississippi State threw the ball into right field.

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After Daniel Cabrera walked on a full count, loading the bases, Mississippi State pulled Ginn from the game. The Tigers soon took a 5-0 lead.

Though the inning ended without another run, LSU had sent 11 batters to the plate, reaching a bullpen also spent from the rest of the tournament.

Pitcher Clay Moffitt walked out for the third inning. A senior whose career has been riddled by injuries, he started because LSU had five available pitchers. He faced one of the top offenses in the conference. He had never started an SEC game.

Moffitt pitched two shutout innings on Friday night. His father Tommy, LSU’s head of strength and conditioning, cheered from the stands, filming with his phone.

Moffitt’s control slipped in the third inning. He walked two batters with one out, and Mainieri brought in junior Aaron George. Though George let in two runs — both counted against Moffitt — he stranded the bases loaded.

LSU took a 12-2 lead with seven runs in the fourth. The Tigers batted around for the second straight inning. They scored six runs with two outs. Mississippi State changed its pitcher three times.

When Reid scored from first base, sliding head-first before the tag at home plate, Moffitt leaned over the edge of the dugout railing. He waved a towel over his head. The crowd chanted “L-S-U” behind him.

Reid came out of the game after he hurt his leg sprinting toward home plate. Broussard had exited earlier with a sore elbow, and LSU played the rest of the game with two players on the bench.

Protecting a 10-run lead, George pitched two shutout innings. So did Chase Costello. Neither had an ERA below 7.00 before the game. Costello sauntered off the field as he ended the sixth, bobbling his head.

LSU played for the fourth time in as many days. It had already used its most reliable pitchers. Three of the starters in its original lineup — Beloso, Reid and Broussard — didn't finish the game.

It moved on in the tournament anyway, a couple players hugging while they grabbed their bags.

“We’re still here!” Smith chanted as he walked through the dugout. “We’re still here!”

Follow Wilson Alexander on Twitter, @whalexander_.