Converting a set piece at the start of each half — and riding strong play by its backline and goalie Lauren Castle — the Ridgefield High girls soccer team won its state tourney opener Thursday.

Seventh-seed Ridgefield edged 10th-seed Southington, 2-1, in a Class LL second-round game at Tiger Hollow. Ridgefield (13-3-3), which received a first-round bye, will now play second-seed Enfield in the quarterfinals on Saturday (3 p.m.) at Enfield High School.

After remaining unbeaten through its first 11 games (9-0-2) this season, Ridgefield faltered, going just 3-3-1 over its last six games, including a 1-0 loss to Staples in the FCIAC semifinals.

During the team’s undefeated start, the Tigers' formula was clear: Use central defender Claire Middlebrook to create or finish goals off set pieces and rely on a tough and seasoned backline to preserve leads. But as the season progressed, Ridgefield had difficulty scoring, with quality chances off set pieces noticeably absent.

In Thursday's contest, the Tigers got back to doing what they previously did best.

Just two minutes into the game, Middlebrook found herself at the receiving end of a Caitlin Slaminko corner kick, heading the ball into the left side of the Southington goal for an early 1-0 lead.

“It was a perfectly served ball and I knew I could use my height and position to put it in the goal,” said Middlebrook. “My mindset was just to open up states with a goal, and fortunately I delivered.”

Four minutes later, Southington answered on a corner kick of its own. Following a scrum and a failed clearing attempt, a Southington player gained control and deposited the ball past Castle to tie the game.

After the scoring trade-off, Southington’s offense remained relatively ineffective for much of the first half. Ridgefield exerted control, with Slaminko, freshman Faith Arnold, and sophomore Megan Klosowski leading the attack.

Twelve minutes into the game, Slaminko cut the ball back to find Klosowki in the center of the field. Klosowski sent a pass to Arnold on the left side for a shot on goal. It was the first of multiple opportunities  by Arnold, who gave the Southington defense a test throughout the game.

Two minutes into the second half, Middlebrook's free kick resulted in a scrum in front of the Southington goal. Slaminko came away with the ball and put a shot in the back of the net to put Ridgefield ahead, 2-1.

From there, it was the sensational play of Castle that preserved the lead. In the 57th minute, she made a diving save after a Southington corner kick resulted in a shot headed toward the left side of the net. Two minutes later, Castle added another diving stop to deny a one-on-one offensive chance for Southington.

With 13 minutes left, Castle came through yet again by blocking a shot from close range. The rebound went to Middlebrook, who cleared the ball on what was to be Southington's last good chance of the afternoon.

“Coming into the game we weren’t entirely sure what to expect because we’ve never played Southington before, but we did have some notes on them and how they play from watching other games,” said senior midfielder Emma Jacobson. "Jobs were given to everybody on the field, and I think we all did a fairly good job at executing them.

“This extended our undefeated streak at home to 28 games, which we take a lot of pride in because it shows how hard we work to defend our home field,” added Jacobson, and “obviously it’s exciting to be moving forward in the tournament.”