GREENWICH — Watching the Greenwich High School girls volleyball team keep its opponent on the defensive was nothing new to Steve Lapham during Tuesday’s FCIAC Tournament quarterfinal-round match against Darien, yet the Cardinals coach couldn’t help being surprised at just how efficient his squad was.

“The first set we came out ripping it, I haven’t seen us hit the ball that clean,” Lapham said. “Offensively, by far, that first set was the best we’ve played all season.”

The host Cardinals outdid themselves in the opening set, rolling to a 25-4 victory — a win that helped catapult them into the conference tournament’s semifinals. Top-seeded Greenwich added another decisive victory to its ledger, defeating eighth-seeded rival Darien 3-1 in the FCIAC quarterfinals.

Greenwich, which won the match by set scores of 25-4, 25-14, 19-25, 25-12, plays fourth-seeded Brien McMahon in Thursday’s FCIAC semifinals at Fairfield Ludlowe High School.

“We really came out fired up and had a really strong offense, probably our strongest all season,” said GHS senior tri-captain/outside hitter Morgan Rafferty, who recorded a team-high 17 kills. “We played some great sets and executed very well. Our offense was great.”

Senior tri-captain/outside hitter Nadia Sotgiu registered a team-best 23 service points, including seven aces, and added 14 kills and nine digs for the Cardinals (18-1). Both Sotgiu and Rafferty were recently announced as All-FCIAC First Team selections.

“We knew it was going to be a tough game,” Sotgiu said “Even though Darien was seeded eighth they are still Darien and they always come out strong, so we knew we had to fight for every point. We really pulled together as a team.”

The Blue Wave (9-10), who lost to Ludlowe in last season’s FCIAC Tournament final, received three kills and two blocks from junior Caroline Martzolf.

“Their communication was very good and their shot placement was also very smart,” Martzolf said of Greenwich. “We have to work on our energy and our communication on certain points.”

Sotgiu’s 13 consecutive service points enabled Greenwich to jump out to a 16-1 lead in the first set. Rafferty posted two kills, while junior setter Nicole Wood had a kill and a tip during the Cards’ big run. Wood tallied 34 assists, senior tri-captain and libero Micaela Lew had seven digs and junior middle hitter Erika Hauschild notched nine service points with two aces for the victors.

“With our serving, we knew we needed to get every serve in and not make unforced errors,” said Cardinals senior Suzanne Goodnow, who provided strong serving throughout. “We tried to keep with the strategy of getting the ball in every single time and keeping it in.”

The second game was closer, but Greenwich pulled away behind several kills from Rafferty and by keeping the pressure on the Blue Wave. Hauschild served out the second set, giving the home team a 2-0 advantage.

The Blue Wave’s best moments came during the third set. The visitors held leads of 11-5 and 18-12 en route to cutting Greenwich’s lead to 2-1. Senior Maddie Corman’s ace closed out the second set.

“The third set we just had the mentality that we had nothing to lose,” Blue Wave senior libero Susie Alpetkin said. “We went out there wanting to compete and started placing shots well and began finding holes and putting balls down.”

Greenwich, however, wasted little time in regaining the momentum. Nine consecutive service points by Sotgiu, coupled with a pair of kills from junior middle hitter Tara Ford put the Cards on top, 11-2. Lew sealed the victory with an ace.

“The most important part of the match was the way we reacted to what happened in the third set,” Lew said. “Volleyball is a mental game, so you have to be mentally tough and focused. This was one of our best games as far as offense and pressure.”

Said Lapham: “Anytime we can come away with a victory against Darien it’s a huge accomplishment. We have to learn from that third set. These games are too big and you don’t want to provide any momentum changes.”

Senior Thea Bolton contributed two blocks and one kill for Darien, which turns its attention to the state tournament. Greenwich, which last won the FCIAC title in 2013, shifts its focus to its semifinal-round matchup against McMahon.

“Our team is really excited and we have a lot of expectations for the postseason,” Sotgiu said. “If we just stick to our game plan, keep pressure on teams, keep our serves tough and hitting spots, I think we can go far.”

david.fierro@scni.com; 203-625-4423