SACO — It was a stand that defined a season. And the Thornton Academy football team was up to the challenge.

On fourth down and with the season on the line, the Thornton defense shut down South Portland running back Joe DiBiase on the 1-yard line, sealing a 20-15 win for the Golden Trojans over the Red Riots, and cemented a spot in the Western Class A championship game.

Thornton (9-1), the No. 2 seed, will travel to Boulos Stadium in Portland on Saturday at 12:30 p.m. to play against Cheverus (10-0), the No. 1 seed in Western Class A.

“It’s fantastic to go this far,” Thornton co-captain Tyler Danley said. “Any team to go this far, going to the Western Maine finals, is going to be great. After our season last year, getting destroyed in the first round, coming back, rebounding this year and going this far, it’s fantastic.”

The win also meant revenge for the Trojans, who suffered their only regular season loss to the Riots in a 20-16 contest back on Sept. 9.

“It’s a great win,” Thornton head coach Kevin Kezal said. “Come playoff football, you’ve got to play a full 48 minutes, and fortunately, we made enough plays at the end to get the win.”

It seemed fate might have been on South Portland’s side, as two penalties by Thornton, including a pass interference called on linebacker Bobby Begin, set up a firs-and-goal situation at the 4-yard line.

The Riots killed 6 minutes and 26 seconds on the final drive of the game. South Portland found itself in a desperate situation, stuck in a fourth-and-14 on the Trojans’ 40-yard line. But Salvatore hit Dan Medici on a fade route, giving the Riots continued life. Four plays later, and the Riots were again stuck in a fourth down situation, this time at the Trojans’ 13-yard line. Salvatore threw an interception to Libby in the end zone, but Begin bumped a South Portland receiver before the ball was thrown, and was called for pass interference, giving the Riots a first down with seconds remaining.

Thornton shut down South Portland on the first three plays. On fourth down, DiBiase was given the ball on a stretch run, trying to run around the Trojans’ defense. But he was swarmed by a host of defenders at the 1-yard line, ending the Riots’ season.

“We knew he was going to do that, he had been doing it all game,” Begin said. “They tried to fill the gap, so I took on the fullback, and I saw the ball go outside. I see open field, and I get nervous. But then two players, I don’t know who it was, but I saw them kill him. I saw them come out of nowhere and take him right out at the 1-yard line. That was the greatest experience of my life.”

In a game where Thornton held a 14-6 lead at halftime, South Portland out gained Thornton 175-61 in offensive yards in the second half, but just couldn’t get enough points on the board to win.

“We settled down (in the second half),” South Portland head coach Steve Stinson said. “But Thornton had a good football team. It’s not easy sledding against them. They’re very good.”

Thornton scored the first touchdown of the contest when Andrew Libby took the shotgun snap out of the “Wildcat” formation and ran 11 yards up the middle of the Riots defense for a score. The extra point by Brandon Briggs gave the Trojans a 7-0 lead.

But South Portland answered back early in the second quarter, capping an 11-play, 75-yard drive with a 2-yard touchdown run off a play action by Riots quarterback Michael Salvatore. The extra point by Brendan Horton was blocked by Andrew Libby, allowing the Trojans to keep a 7-6 lead.

Thornton scored two possessions later, when the Trojans put together an 11-play, 53-yard drive, which ended with Libby plowing ahead on a 1-yard touchdown run. The extra point by Briggs gave Thornton a 14-6 lead, where it remained until halftime.

South Portland put points on the board quickly to start the second half, when Horton kicked a 21-yard field goal to cut Thornton’s lead to 14-9. The Riots began driving on their next possession, Thornton cornerback Kyle Forbes jumped on a slant route and intercepted a Salvatore pass, giving the Trojans the ball at the Riots’ 34-yard line. Five plays later, Thornton quarterback Eric Christensen connected on a 22-yard touchdown pass to tight end Dakota Tarbox, giving the Trojans a 20-9 lead.

South Portland scored on the next drive, moving 78-yards down the field on 11-plays, before DiBiase snuck into the end zone on a 1-yard touchdown run to bring the score to 20-15. The Riots never scored again.

As the clock hit zero, the Trojans stormed the field in celebration.

“It feels amazing,” Tarbox said. “Every time we come out here, we play for the next 48 minutes, and our boys went out and got it done.”

DiBiase ran for a game-high 104 yards on 29 carries. Salvatore finished 12 of 22 for 137 yards.

The Trojans were led offensively by Libby, who rushed for 68 yards on 16 carries. Tarbox had three catches for 38 yards.

— Contact Dave Dyer at 282-1535, Ext. 318 or follow on Twitter @Dave_Dyer.