LSU’s most costly blunder Saturday came two hours before Vinny Esposito took Caleb Gilbert’s 3-0 pitch for the go-ahead sacrifice fly in a 5-4 loss to Sacramento State.

The big gaffe came in the third inning, when Brody Wofford stood on third base with one out and four runs already in. Greg Deichmann had the opportunity to pile on Hornets senior left-hander Grant Kukuk.

Deichmann struck out on four pitches. Mike Papierski followed with a groundout, stranding his teammate, Wofford, at third base.

Two games earlier, Deichmann bounced into a fielder’s choice before O’Neal Lochridge struck out to end an eight-run second inning against Lamar — again, with a runner standing on third.

“That’s two games in a row we’ve had a chance to bury them early and we left a runner on third base with one out and gave the other team momentum,” LSU coach Paul Mainieri said. “They rallied to come back in the game. ... Had them on the ropes, let them off, they stayed in the game. In fact, they gained momentum from getting our hitter out. We didn’t score and it allowed them to have life. (They) stayed in the game and chipped away and eventually caught up with us.”

LSU wasted more opportunities. Kramer Robertson was left on third and Antoine Duplantis on first in the seventh when Jake Fraley and Wofford flew out.

Deichmann reached third in the eighth but was thrown out at home on a Lochridge fielder’s choice.

In all, the Tigers were 4-for-17 with runners on base and 3-for-12 with runners in scoring position.

“It’s a product of a guy not coming through in the clutch for us,” Mainieri said. “It’s part of baseball. Their pitcher beat our hitter at a time when we needed our hitter to come through. It turned into a barnburner, and we had a couple bad breaks at the end. Consequently, we suffered the consequences of it.”

Gilbert skirted damage in the seventh and eighth innings to protect a slim LSU lead, but he issued back-to-back singles — the second of which tied the game — and allowed Esposito’s sacrifice fly one batter later.

Again, it was a similar prospect for Gilbert, who came into the Lamar game with the bases loaded and nobody out Wednesday. He notched two strikeouts before issuing a two-strike, game-winning RBI single in a 12-11 loss.

“I should have made a better pitch,” Gilbert said of his ninth inning. “Then they strung together a couple hits. I had to get back in the zone, mentally and physically I guess. It just wasn’t enough.”

Cole Freeman, the Tigers’ new everyday shortstop, was injured on the first play of the ninth inning — a Chris Lewis grounder that Freeman had issues handling. Mainieri didn’t have an update on Freeman after the game, only saying he got hit in the “wrong place.”

Gilbert, a true freshman, entered in the seventh inning in relief of Riley Smith, who allowed consecutive one-out singles to put the go-ahead run on board. Gilbert need four pitches to strike out Matt Smith before inducing a flyout to strand the runners.

Deichmann booted Gunner Pollman’s soft grounder to begin Gilbert’s eighth inning, and pinch runner Blake Edmonson got to third on a wild pitch and stolen base. Gilbert walked Brandon Hunley, and pinch runner James Outman ended up at second on the wild pitch.

No. 9 hitter Bronson Grubbs attempted a squeeze bunt, which rolled straight to Gilbert, who flipped to Mike Papierski for a crucial second out. A strikeout of leadoff hitter Andrew McWilliam followed to quell the threat.

“You have to have defense behind you, too,” Mainieri said. “You got a routine ball in the eighth inning that was erred and forced him to throw a bunch of extra pitches. Then he gets a routine ball to lead off the ninth inning and he kicked it.

“Going into the season, I was very concerned with our infield defense, and today we didn’t make the plays when we needed to, and it put a lot of pressure on him. (Gilbert’s) going to be great, I’m telling you.”

Mainieri stacked the middle of his order with five left-handed hitters against Kukuk, and in a four-run third inning, those five hitters produced. Duplantis, who finished with four hits, had an RBI infield single, Fraley an RBI double and Wofford a two-run triple that eluded Andrew McWilliam’s glove.

LSU mustered just four hits after that third-inning uprising, two from Duplantis.

Starter Alex Lange lasted just five innings, the victim of an inflated pitch count and erratic control. He issued three walks and gave up three earned runs — one short of tying his career high — including a mammoth solo homer to Esposito to lead off the fourth, capitalizing on the momentum from the Tigers’ inefficient hitting in the previous inning.

“This team was fighting from behind at the beginning,” Lange said. “I take full responsibility for this loss.”