DARIEN — The Westport U10 softball team had plenty of experience battling Darien over the past several seasons, but it hadn’t come out on top too often.

When it mattered most in the Section 1 title game on Saturday at Darien’s home field, Westport needed to play flawless softball to upset the familiar foe; and did so behind the left arm of Morgan Carnahan.

Carnahan held Darien to three hits in a pitcher’s duel with Darien’s Brooke Romano, and got stellar defensive support as Westport outlasted Darien 2-1 to claim the Section 1 title.

“I think this is a huge upset,” Westport coach Lou Alfero said. “We’ve played this team 20 times in travel in the last three years and we’ve won one game. We came in as the underdog pretty loose; I think they played very loose. There was no tension on that bench at all.”

Westport, which claimed the District 2 title last week, moves on to compete in the four-team state championship tournament beginning on Wednesday at 5:30 p.m. at Unity Park in Trumbull.

Darien was two bases away from tying the game when Romano laced a single to the outfield and reached second on a passed ball. Carnahan got one more put out on a ground ball to shortstop Grace Alfero.

“We made it real close at the end,” Darien coach Antonio Romano said. “We’re one hit away; I think for a bunch of 10-year-old girls they played a heck of a game.”

Kate McDonald provided the big hit for Westport, an RBI double in the top of the second that tied the game at 1-1. She would later score on an RBI groundout by Chloe Hackett.

“I changed the lineup last night and moved (McDonald) up one spot,” Lou Alfero said. “She had been swinging the bat really well; we didn’t put up 15 runs, but I was hoping this would be a close game.”

Both teams opted to rest their aces during their pool play meeting Thursday as both had sealed spots in the championship game. Darien won 10-1 with Romano and Carnahan well rested.

Both teams put on a defensive clinic which would not have been out of place on the Darien varsity field during the spring high school season. Both right fielders — including Westport’s Olivia Stubbs in the bottom of the fifth — robbed the opposition of an extra base hit in the late innings.

The hosts jumped out to a 1-0 lead in the bottom of the first inning on an RBI groundout by Kate Avitabile. With Darien threatening for more runs in the frame, it ran into an out on a walk that would have put runners on the corners.

“I think in the first inning we played our game,” Romano said. “We played aggressive in our base running; I think both pitchers settled in and usually good pitching stops good hitting.”

Darien — the District 1 champions — came into the game averaging double digits in runs and hits prior to running into Carnahan. Carnahan struck out five batters and retired 15 in a row between the end of the first and two outs in the sixth.

“(Carnahan) was amped up, she knew it was a big game,” Alfero said. “She had two or three really quick innings; we had a couple of first pitch groundballs. Our defense was absolutely incredible today.”

rlacey@bcnnew.com