LATHROP — Lathrop High head coach Nathan McGrath could sense it from the Spartan Nation cheering section moments before Wednesday’s Sac-Joaquin Section Division IV playoff opener against 11th-seeded Mariposa.

The lively bunch was loud to begin with but yearned to have something truly to cheer about. This was the school’s first-ever postseason basketball game on campus, and the sixth-seeded Spartans tallied their first-ever postseason win, 52-37.

“I told our guys before the game to get that crazy crowd into it,” McGrath said. “This school has been dying for something like this. Get that crowd in a frenzy, get your bench in a frenzy and let Mariposa know they’re in for a tough night.”

T.J. Conley, Lathrop’s active 6-foot-3 center, answered the call. While the other nine players on the court played tight to start, he carried the Spartans to an 11-3 first-quarter lead and helped spark a decisive 16-0 run in the first half when he registered six points, eight rebounds and five blocks.

Conley’s crowd-pleasing plays were his two dunks — first in transition early in the opening quarter, then a demonstrative two-handed slam in traffic off a perfect entry pass from Nilo Yuson to start the scoring in the second. Yuson capped that 16-0 barrage with a highlight-worthy layup in transition that made it 19-3 with 4:37 left in the half.

“I pretty much came out loose with my goals set,” said Conley, who finished with 14 points, 14 rebounds and five blocks. “I was thinking about this game all week, went to sleep dreaming about it and woke up thinking about it every morning. I knew I had to get rebounds and play well defensively, and I got my game dunks in.”

Yuson added 12 points, eight assists and three steals. Nicholaus Obazuaye chipped in 10 points, six boards, four assists and three blocks. Eric Spencer keyed the Spartans (17-10) off the bench, contributing eight points, seven rebounds and three blocks.

Lathrop’s all-around length bothered Mariposa in the first half when it totaled 10 blocked shots. That forced the Grizzlies to settle for perimeter shots, and even some those attempts were well off the mark. The mere presence of Conley and Spencer were enough to change shots no matter where they were coming from.

“When T.J.’s confidence is high he is a completely different player,” McGrath said. “Conley was the tone-setter tonight, for sure.”

Yuson, meanwhile, was the steadying influence when he mustered enough energy to stay on the floor. It was a gutty effort by the senior, who played through a 103-degree fever.

“It was tough but I knew it was a big game,” Yuson said. “(The crowd) really pushed us tonight and showed great support. It really made us want to play better for them.”

McGrath didn’t want to overwork his crafty point guard in the second half, but the Spartans were already down starting small forward Isaiah Ellis, who reinjured an ankle that sidelined him for most of Lathrop’s pre-league schedule. Ellis turned the ankle after making a layup with 5:53 to go in the second quarter. He finished with four points and four rebounds.

“I tried to limit Nilo (but) we go as he goes, we really do,” McGrath said. “It’s no secret; we’re not a super deep team. We had our No. 3 (scorer) out, probably for the rest of the playoffs, and a sick point guard, so we had to scratch and claw tonight.”

Mariposa (23-4) also forced McGrath to play Yuson more than he wanted to.

Down 29-7 early in the third, the Grizzlies answered with a 12-3 burst to get to within striking distance. Jadin Battles scored nine of his game-high 17 points in the period, and Mariposa twice shrank the deficit to single-digit margins early in the fourth.

An 8-0 flurry topped off by a Conley jumper with 1:39 left sealed it for Lathrop. Sam Tucker, Mariposa’s leading scorer for the season at 11.6 points per game going in, was held scoreless throughout.

“You have to give them credit, that’s a long drive and a big crowd to face in foreign territory,” McGrath said of Mariposa, the Southern League champion that had a 16-game winning streak snapped. “They didn’t have their ‘A’ game to start but they came to play in the second half and made us work. 

“They could have easily folded the tent and they didn’t. They’re not a bad team and they are young with a bright future ahead of them.”

The future is now for the upstart Spartans, who have now won six of their last seven. They will take their momentum to No. 3 Riverbank on Friday. The Bruins (22-3) shelled Summerville 70-47 in their first-round contest.

“We have nothing to lose right now,” McGrath said. “We were one game from not making the playoffs and look at us now: first home playoff game in school history and first playoff win. It’s something to be proud of, but now it’s time to get stingy.”