SOUTH BERWICK — Marshwood High’s football team showed the grit and poise that has defined its season in a 32-16 win Friday against Kennebunk to earn the top playoff seed in Class B South and a bye into the regional semifinals.

The Hawks rebounded from their lone poor effort this season, a 37-14 home loss to Biddeford. They also bounced back during Friday’s game. Kennebunk led 10-0 in the first half and 16-8 early in the third quarter. Plus, Marshwood’s top player, running back/linebacker Greg Castoras, was on the sidelines in street clothes, wearing a coach’s headset with a video tablet in his hands, encouraging teammates.

“They responded to some adversity. We had a tough game last week and we had some tough conversations about the film, and how we practiced,” said Marshwood’s interim head coach, Andrew Elwell. “We needed that reality check. I needed that reality check. And I could not be more proud of the kids.”

Marshwood, with a 35-man roster, finishes the regular season at 7-1. With a welcome week off, the Hawks are hopeful to have Castoras back in two weeks when they host the winner of the No. 4 vs. No. 5 quarterfinal, likely Falmouth vs. Westbrook.

“We just put our heads down and worked,” said Michael Sbrizza, the Hawks’ senior quarterback/safety/punter/kicker. “That’s all it comes down to really. Work, work, work. It’s all about the process. And I think it showed here tonight.”

Kennebunk, at 6-2, will also get a bye into the regional semifinals. Biddeford (5-3) had an opportunity to jump to No. 2 but was beaten 44-8 by Cheverus (3-5), which needed the win to earn a playoff spot.

“Any time you can advance a week without playing, that’s obviously a benefit,” said Kennebunk coach Keith Noel. “After tonight, it gives us a chance to get back to basics. Which we’ve got to go and do. Get some guys a little healthier and be ready to play in two weeks.”

Early in the third quarter, both teams scored on long touchdown runs. Kennebunk’s Bradley Farrell took the third scrimmage play of the half 43 yards to put the Rams up 16-8. Farrell also had a 66-yard score in the first half.

On the next possession, Sbrizza turned a QB sneak into a 39-yard score, and Noah Goodwin’s conversion rush knotted the game at 16-16.

Both defenses stepped up after that, resulting in five consecutive three-and-outs, three by Kennebunk.

Marshwood appeared headed for another punt when, on the first play of the fourth quarter, Goodwin took the second handoff on an inside criss-cross counter — a staple play in the wing T offense for both teams — and went 24 yards on second-and-17. Later in the drive, on third-and-15, Sbrizza connected with Parker Ferrer for a 21-yard gain to the Rams 7.

On fourth-and-goal, Goodwin capped the 11-play drive, scoring from the 1.

Sbrizza, as he had done throughout the game, cued up a squib kickoff. This one caromed off a front-line Kennebunk player and was recovered by Marshwood’s Harrison Ames. The Hawks then put together a 10-play touchdown drive.

When Goodwin scored from the 10 and Jon Buttrick added the 2-point conversion, Marshwood led 32-16, only 1:40 was left in the game, and Kennebunk had not run a play in the fourth quarter.

Buttrick, a 5-foot-7, 150-pound junior, stepped into Castoras’ starting role on both sides of the ball. He had a team-high 17 carries for 59 yards, including an 11-yard first-half touchdown. On defense, he had multiple tackles for loss, including a sack.

Buttrick grew up playing football but said he initially chose not to play this year to focus on wrestling. He said Elwell was constantly recruiting him during school. He joined the team after the second game of the season.

“The first couple of weeks, I was mostly a practice player, helping out as much as I can,” Buttrick said. “Definitely, my role was very small. Castoras, our best guy out there, went down last week. Basically, Thursday, I found out (I’d be starting). I wasn’t too surprised. I was of the mindset, ‘Next guy up.'”

• Kennebunk: Peter Landenberger (13 carries, 81 yards), Bradley Farrell (four carries, 109 yards, two TDs), Giovanni D’Elia (3 of 11 passing, 35 yards), Blake Morris (35-yard field goal)

• Marshwood: Noah Goodwin (13 carries, 71 yards, two TDs), Michael Sbrizza (12 carries, 71 yards, TD; 2 of 11 passing, 30 yards, one INT), Jon Buttrick (17 carries, 59 yards, TD)