LYNN — If the season is a roller coaster, these two teams have been enjoying the fun trip down for a while now.

After bumpy beginnings, St. Mary’s lacrosse team won 11 of 12 games to conclude its regular season, while Saugus triumphed in eight of its last 11.

But in Friday’s Div. 3 state tournament showdown, one side had to fall. The No. 24 Spartans (13-5) defended Manning Field with a convincing 20-2 victory against the No. 41 Sachems (8-8).

“They know ground balls win games, turnovers are a sin, and to find the open guy,” said St. Mary’s coach Brendan Forrest, whose group will battle No. 9 Hanover. “Someone’s always open.”

Saugus struck first when Franklin O’Leary scooped up a loose ball and fired one in. Eighth grader Gavin Diozzi also ripped twine, taking his bigger opponent one-on-one early.

“He (Diozzi) had a great game,” said Saugus coach Clint Arsenault, “and then I have three seniors — Hunter Arsenault, Larry Barrows, and Koby Jette — who played the last games of their high school careers.”

Featuring shoulder-pad crunches and the occasional loose stick, Friday’s game grew in physicality after the first few minutes.

St. Mary’s, finding its odd-man rushes, took a 2-1 lead. Finn Racki then scored a laser from distance before Sal Brogna added another 13 seconds later as the Spartans led 5-2 after one.

“Unbelievable,” Forrest said. “Sal, Finn Racki, and Dalton Diozzi have been phenomenal all year long.”

Saugus goalie Barrows stoned a three-on-two chance during the second quarter. James Caruso caught eyes when he dangled through a pair of defenders, and Moises Guadalupe Perez showed a strong stick to break up a St. Mary’s possession.

“The boys battled to make the playoffs. You can’t be upset and we played with a short team,” Clint Arsenault said. “We finished with 11 players because a kid got hurt, so it was a great effort all season.”

Talk about unselfishness — and perhaps a case of déjà vu. Dalton Diozzi had two scoring opportunities during the second quarter, but made extra passes to Shea Pawl for a pair of St. Mary’s goals.

With Brogna and Racki taking charge, the Spartans took a commanding 12-2 lead into halftime.

“If we can take some time off the clock and let the ball do the work, it becomes really important,” Forrest said. “Also, Adam Fila has been phenomenal for us. He never even played goalie, but hopped in.”

Forrest applauded a strong season from the Sachems, who returned to the state tournament.

“They have some great players and the fact that they’re growing their program is awesome,” he said. “Saugus has always had athletes and that’s important. Their coach (Clint Arsenault) is really bringing them along.”

Next in St. Mary’s championship quest: Hanover (10-8).

“Everything’s going to be harder and the pyramid gets really hard,” Forrest said. “We’ve got to limit turnovers, win every ground ball, and possess.”