WESTWOOD — If this was the appetizer, one can only imagine what the main course will be like.

Xaverian Brothers High School and St. John’s Prep squared off Thursday at the Hawk Bowl in a game for the ages. The Hawks won, 23-21, on a 29-yard field goal by junior Luke Bell with three seconds left. But it was only possible thanks to a wild final minute that was as confusing as it was thrilling.

The two teams will square off again Wednesday night (8) in the Division 1 Super Bowl at Gillette Stadium. But any assumption that The Prep and Xaverian would ease up on the throttle because of that certainly proved specious.

“Anyone who thinks that knows zero about football,” said Xaverian coach Al Fornaro.

“People who said this would be a JV game don’t know what they’re talking about,” said Prep counterpart Brian St. Pierre. “It was a good, competitive game between the two best teams in the state.”

St. John’s led, 21-20, with five minutes to go when things began getting weird. Xaverian was knocking on the door when St. John’s defensive back Grayson Ambrosh picked off Henry Hasselback (son of former NFL quarterback Matt Hasselbeck) in the end zone with a minute and a half left.

Game over, right?

“No,” said Fornaro. “We knew we’d need either a stop or a turnover.”

Xaverian got the stop, forcing St. John’s to a three-and-out. On the snap preceding the punt, the ball sailed over Jack Hayes’ head and rolled into the end zone for what looked to be a safety. But Hayes rescued the ball, ran out a couple of yards, and his quick kick rolled all the way to the Prep 43 with 59 seconds left.

That was more than enough for Hasselbeck. On a fourth-and-5 from the 38, he found Christian McIntyre and the play was good for a first down. But not without controversy. Even Fornaro thought there should have been a measurement.

“I asked the ref, but he said ‘no, it’s a first down,’” Fornaro said. “I wasn’t going to argue after that.”

St. Pierre respectfully disagreed.

“It was significantly short,” he said. “And I’m upset about it. I don’t know why they didn’t do a measurement on that.”

From there, Hasselbeck and Xaverian worked the ball down to the Prep 20 and Bell connected on the field goal with yards to spare.

“He (Hasselbeck) made a great run to set up the field goal,” Fornaro said. “He is definitely our X-factor.”

St. John’s (10-1) suffered its first loss of the season for two reasons: Xaverian running back Mike O’Connor, and the Eagles’ failure to get off the field on third- and fourth-down plays. Xaverian converted on eight of 11 third-down tries.

“We couldn’t get off the field on them, and you can’t do that against a good team like Xaverian,” St. Pierre said. “That’s something we definitely will work on this week.”

O’Connor, who began the season as Xaverian’s No. 2 back, ran for 193 yards on 17 carries and scored two of Xaverian’s three touchdowns, one on a 6-yard run that he set up with a 38-yard scamper to give Xaverian a 6-0 lead. He followed that up with a 72-yard rush, also in the first quarter to make it 14-7 Xaverian (Prep quarterback Deacon Robillard scored on an 18-yard run in the meantime).

Things quieted down in the second quarter and the Hawks led 14-7 at the half.

However, principal Prep back Cam LaGrassa, who split time with Jeff Quigley, rushed for 24 yards out of the gate in the third quarter, and Robillard completed the drive with a 15 yard run. Quigley, who got the bulk of the carries, ended up with 84 yards on the ground.

“He’s worked very hard,” said St. Pierre. “He deserved to play.”

After St. John’s got a stop at the Xaverian 38 on a fourth-down try, Robillard found Gavin Gold for 17 yards to give St. John’s a 21-14 lead.

But Hasselbeck’s 52-yarder made it 21-20, and the PAT attempt was blocked. And when Ambrosh picked off Hasselbeck, that looked as if it would be enough.

“I don’t think we played poorly,” St. Pierre said of the team’s effort, “but we could have played better.”