For a team that has hardly been tested for much of the season, Lathrop is somehow unflappable when the going does get tough.

The fourth-seeded Spartans were pushed by a squad as scrappy and athletic as themselves Tuesday in the first round of the California Interscholastic Federation Division III

“I think I’m more nervous than my boys and they always tell me, ‘We got this, coach,’” Lathrop coach Toa Fa’ali’i. “But I told them we cannot put ourselves in a hole and find ourselves trying to get back into the game.

“Today was that kind of day and it happens, but I’m glad they pulled through and I believe in them. They can go to a fourth set or even go all five. I have confidence in my boys.”

Lathrop (31-0) also won three highly-competitive sets in capturing its first-ever Sac-Joaquin Section championship this past Saturday. Next is a trip to Oakland for a semifinal against top-seeded Bishop O’Dowd on Thursday.

“I know we’re good, but it’s the playoffs,” Fa’ali’i said. “Moreau Catholic is really good and I’ve seen Bishop O’Dowd on video and they look really good. It’s nice to play teams from the Bay Area, and it feels good to win against teams like that.”

The Spartans started slow in every set Tuesday but always found a way to make a run at the end of each. The Mariners (21-11) from Hayward jumped ahead 8-3 in the opening set after a kill from Dylan Parreno.

Lathrop did not lead until a hitting error from Moreau Catholic vaulted the home club ahead, 19-18.

Christian Green came up with a rally-capping kill to keep the Spartans’ momentum surge going. Christopher Millan and Arman John later combined to block Nolan Hatcher to tie it at 23-all. The Mariners committed another hitting error, and John locked up Game 1 for Lathrop with a hit that was deflected out of bounds.

“It’s just chemistry,” John said of the comeback. “We started together at Mossdale School four or five years ago. Without our chemistry, I don’t know if we would have made it this far.

“Honestly, I truly believe we were nervous since we’ve never been in a situation like this. During our freshman year there were no fans. Now, we have all these fans for big matches so we get a little nervous. We managed to push out of it.”

Ultimately, the Spartans’ hard-hitting trio of Jerico Santillan (12 kills, four digs), Green (16 kills, seven digs) and John (11 kills, six digs) came up with big spikes at key moments. Tory Sumbler racked up 42 assists.

John again got the clinching point to end the second set, but it was his earlier run of three straight kills that sparked the Spartans. The third kill of that streak required a mid-air adjustment from John, who slapped it down with his weaker left hand. That gave Lathrop a 16-14 lead.

“I love being the one who gets those kills,” John said. “That energy feeds me to want just kill every ball that I see.”

Moreau Catholic staked another 8-3 lead in the third set, but unforced errors helped keep Lathrop in it early.

The Spartans began take over midway through the game, as Mariners coach Jerico Abanico called a timeout after Aaron Obasuyi roofed Parreno at the net to close Lathrop in, 15-14. Back-to-back kills from Green and Santillan gave the Spartans a 22-19 lead, forcing Abanico to burn another timeout.

John and Green closed the show with successive kills.

Abanico said that an injury to his starting setter, who tore an ACL on the Mariners’ senior night, has made things tough in their postseason. They finished as the Division III runner-up in the North Coast Section, dropping the final to Bishop O’Dowd in three sets after previously downing that same team in four.

“Our starting setter today is two months into the game and he’s a converted basketball player,” Abanico said. “Considering the level he is at he wasn’t that bad, but there could have been better decisions when it came to where to set and whom to set on the play. Honestly, Lathrop has a good, consistent team and I think that added something to that.”

Bishop O’Dowd (32-4) defeated No. 8 Central of Fresno, 25-19, 23-25, 27-25, 25-19.

“Honestly, I’m rooting for Lathrop, right now,” Abanico said. “I’m biased because (Bishop O’Dowd) is one of our rivals, but I think if Lathrop can really stay consistent they’re going to give Bishop O’Dowd a match. Bishop O’Dowd is a really good team, but I think Lathrop matches up pretty well with them.”