TRUMBULL >> Stamford coach Mike Smeriglio has felt all season playing the tough competition in the FCIAC could only help his team when the postseason rolled around. Smeriglio might have been right.

With a dominant effort from 6-foot-2 junior Andrea O’Connor, and capitalizing on numerous Amity errors, third-seeded Stamford upset second-seeded Amity 3-0 in the Class LL semifinals Wednesday evening at Trumbull High.

The 25-16, 25-20, 25-22 victory propelled the Black Knights to Saturday afternoon’s final against fellow FCIAC member and fourth-seeded Ridgefield, an upset winner over top-seeded Greenwich, at East Haven High at 4 p.m.

“I feel we are the best conference in the state,” Smeriglio said. “We play Ridgefield, Greenwich and others. When you play a schedule like that, it gets you ready for this.”

Stamford, which also took home the FCIAC tournament title, returns to the state final for the first time since 2000, when it fell to Fairfield in the Class L title match.

“It feels great to get there,” O’Connor said after finishing with 13 kills, seven service points, six blocks and four aces. “I have never been there in volleyball. I have been there in basketball. This feels great to get there.”

O’Connor and the Black Knights set the tone of the match early, taking leads of 5-0 and 10-3 in the opening game and never looking back. O’Connor was particularly impressive in the match at the net with her blocks, as she offset the height in front of Amity’s Kathleen Walsh and Abigail Harbinson.

O’Connor, along with seniors Sara Staley and Lisa Balazs, seemed to always be in the right spot, altering the offense of the Spartans.

“She is a really good player,” Amity coach Seth Davis said of O’Connor. “They got her the ball. They did that really well. They are a good team.

“I thought we played well. It is a tough way to end the season. But, only one team ends the season winning.”

The Spartans, (22-2), never led in the opening game, getting only as close as 17-12 and 21-16, before O’Connor fittingly ended the opening game with a pair of aces.

“Andrea (O’Connor) continues to amaze me,” Smeriglio said. “She was able to disrupt them with her blocks and kills.”

Looking to return to the final for the first time since 2003, the Spartans got off to a quick start in the second game, using a kill by Harbinson and three errors by the Black Knights to take a 7-2 lead. Another kill by Harbinson put Amity ahead 14-12, but Stamford was not going away.

An ace by O’Connor and a kill by Lauren O’Neill put the Black Knights on top by one point. Trailing 21-18, Walsh got the Spartans going again with an ace, coupled with a kill by Dani Nordyk to get within 21-20.

Amity never got closer as three errors by the Spartans, along with a booming kill by O’Connor, closed the second game.

“This is super disappointing,” Walsh said. “I am so happy the season went so well and I am proud of how far we got at the end.

“We knew they were strong and they had a big girl (O’Connor) in the middle. They were a strong team.”

Walsh led Amity with 14 kills, nine service points and seven digs, while Harbinson had nine kills, and Nordyk added 11 digs. Jaiden Williams finished with 30 assists and seven digs for Amity.

With the game even at 11 in the third and final game, a kill by Staley and a block by O’Connor started a run which ended with another O’Connor block for a 16-11 lead. Amity got as close as 18-16 with an ace by Harbinson, but O’Connor was there again with a kill to end any hopes of an Amity comeback.

“We work so great together,” Staley said after her team improved to 24-2. “They put up an amazing fight in that last game. This feels amazing.”

Jayla Wilson ran the Stamford offense with 23 assists, Gloria Mattioli had 13 digs, Balazs added seven kills, seven service points and three aces, and Staley finished with six service points, five kills and three aces.