Northwestern State pitcher Cullen McDonald celebrates with teammates after the Demons defeated LSU 3-1 at Brown-Stroud Field in Natchitoches on Tuesday.

NATCHITOCHES — They piled onto the grassy banks above the dugouts and down either baseline, a mass of purple creating one of the largest crowds in the history of Brown-Stroud Field.

Every time LSU plays at Northwestern State, fans come in droves, and Tuesday night was no different. The second-largest crowd in the stadium’s history (3,240) showed up, and they all watched a pitcher shut down the Tigers.

Northwestern State starter Cullen McDonald threw 126 pitches over 7⅔ innings, holding the No. 10 Tigers to one run in a 3-1 run.

Though LSU may have found one its weekend starters in Landon Marceaux, who threw well, McDonald stole the show, leading Northwestern State (8-6) to its first victory over LSU (11-5) since 2011.

“He kept us totally off balance,” coach Paul Mainieri said. “We didn't coach our kids well enough to make the adjustment to the kind of pitcher he was.”

McDonald, who entered the game with a 0.65 ERA, mixed his pitches to clamp down on the Tigers. He did not throw fast, but relying on his curveball and changeup, he kept LSU guessing.

After LSU scored an early run, McDonald retired eight straight hitters. When McDonald strode off the field in the eighth inning to a standing ovation, LSU had runners on first and second. Chris Reid walked to load the bases with two outs.

The Tigers — who have stalled offensively for long stretches over their last four games — had a chance to conduct another comeback. But Daniel Cabrera grounded out, ending LSU’s final scoring threat.

LSU’s pitchers matched McDonald for most of the game. Marceaux, a freshman making his first start since an abysmal outing March 2 at Texas, pitched out of the weekend rotation for the first time. He retired all nine batters he faced.

Mainieri said if Marceaux had pitched five or six innings, he would not be available to start this weekend. Marceaux threw only 31 pitches — 22 for strikes — possibly setting up him to pitch when LSU opens its Southeastern Conference schedule this weekend against Kentucky at Alex Box Stadium.

“I felt like I threw the ball well tonight,” Marceaux said. “This was a big confidence booster after a couple bad outings.”

Mainieri thought most of LSU’s pitchers threw well. But for the third straight game, the Tigers gave up all their runs in one inning.

After Marceaux left the game and Ma’Khail Hilliard threw two scoreless innings, Aaron George entered to pitch the sixth. The Tigers led 1-0. George gave up two singles. Once he walked the bases loaded, Mainieri inserted pitcher Matthew Beck.

Beck recorded two outs. Then a low fastball scooted past catcher Brock Mathis to the backstop. A game-tying run scored. Northwestern State freshman Jeffrey Elkins drove a two-run double into the left field corner. LSU trailed 3-1.

The night belonged to McDonald, and LSU suffered because of it.

“When you're not scoring any runs,” Mainieri said, “that one inning can cost you the ballgame.”

Follow Wilson Alexander on Twitter, @whalexander_.