SACO — After giving up six earned runs in the third inning ”“ one more than he’d previously allowed all season ”“ Cheverus starting pitcher Mitchell Powers had just one goal as he continued to labor through Tuesday’s Western Class A baseball prelim against Thornton Academy: Stay in the game, and give his team a chance.

“It was far from my best stuff, and after that six-run inning, I just had to bear down from there on out and throw strikes,” Powers recalled. “I knew the offense would get us back into the game.”

That’s exactly what Cheverus’ league-leading offense did, scoring five runs over the next two innings as the Stags battled back to take a 7-6 lead, and from there, Powers did the rest, fighting his command throughout but nearly shutting out the Golden Trojans over the final four innings as Cheverus moved on with 9-7 victory at the Thornton Academy baseball field.

The ninth-seeded Stags (9-8) will face top-ranked South Portland in a quarterfinal on Thursday, while Thornton (8-8-1) failed to reach the quarterfinal round for the first time since 2010.

“Earlier in the year, we got down on ourselves when we had to come from behind,” Powers said. “Today, we stuck with it and just put the bat on the ball. That’s all you have to do. It was a great effort by the whole team.”

Powers finished with 113 pitches as he allowed a season-high 12 hits ”“ including five in a row in the six-run third ”“ and consistently struggled to put Thornton batters away after getting ahead in the count.

But the Cheverus senior showed why he compiled a 1.00 ERA this spring in the later innings, working out of jams in the fifth, sixth and seventh innings, and also knocking in a key insurance run late to build his team’s slender lead.

“Powers was OK, but he wasn’t sharp,” Cheverus coach Mac McKew said. “It shows a lot about what kind of competitor he is. Sometimes pitchers have to go out there without their best stuff or best command, and they still win. That’s Mitchell.”

Cheverus backed its ace up with 14 hits off three different Thornton pitchers, scoring at least one run in every inning but the second. The Stags were also helped out by four crucial Thornton errors that led to four Stags runs.

“We hit (Powers) well, we just had our problems in the field,” Petit said. “Either we play good defense and don’t score runs, or we score runs and don’t play defense.”

The defensive troubles started early. Trojans starter Drew Gelinas began the game with an apparent strikeout of Cheverus leadoff man Charlie Mull. But catcher Brandon Hall couldn’t handle strike three in the dirt, allowing Mull to get all the way to second as the ball rolled to the back stop and then score after a Powers sacrifice bunt and Chris Tinsman sacrifice fly.

“That’s frustrating as a pitcher to see an error on that,” Power said. “But we executed on that, which was key.”

Cheverus took a 2-0 lead in the third as Mull’s leadoff double was followed by a Powers RBI single, but Thornton took what looked to be a commanding lead in the bottom half of the inning.

The rally started with No. 9 hitter Mitch Jacques drawing a walk, and the Trojans followed with five-straight singles, including a two-RBI liner to right by Gelinas, to score four runs.

Drew Lavigne’s sacrifice bunt to move runners to second and third was the first out of the inning, and after Justin Cloutier’s RBI groundout, Tinsman’s error on Evan Balzano’s grounder to first allowed Matt Rutherford to score and make it 6-2.

“Sometimes we’re our own worst enemy, and we walk the nine guy to lead off the inning after being ahead in the count,” McKew said. “And then the top of their order has some hitters, and if you get your pitches up, you’re going to be hit.”

But from there, the Stags chipped away, scoring twice in the fourth inning on three singles and a Lavigne error. Three more runs were then added in the fifth as Gelinas ”“ who had outdueled Powers and threw a nine-inning complete game in TA’s 4-3 win over Cheverus on May 29 ”“ was chased from the game after 4.1 innings.

“He was struggling with his curveball, and their guys were sitting on that,” Petit said of Gelinas. “You need more than one pitch to succeed in this league, and he was struggling with that pitch.”

Rutherford came on in relief but got just one out, allowing three hits and a walk as three runs scored, before Ben Lambert came on to strikeout Logan McCarthy with the bases loaded to limit the damage.

“Offense is our thing, and the hitters came around,” McKew said.

Thornton had a chance to retake the lead in the bottom of the fifth, loading the bases with one out, but Powers buckled down to strikeout Balzano and get Conor Purvis to pop out.

Powers then helped himself out with a two-strike, two-out RBI single to right to make it an 8-6 lead, and worked around an error and an infield single to get out of the sixth unscathed.

The Stags added one last run in the seventh, and after allowing two singles to start the seventh inning, a clearly tiring Powers found one last gear, getting a sac fly, a fly out and then striking out Lambert with a 3-2 fastball to end the game.

“The adrenaline started going on that one,” Powers said. “I pretty much just threw it as hard as I could to get that last out. No way did I want him to get on.”

The Stags will now take on No. 1 South Portland, which won the teams’ regular-season matchup behind a one-hitter from pitcher Henry Curran, Thursday’s projected starter.

“We made it tough on ourselves today than we should have but we showed a lot of resiliency,” McKew said. “We’re just glad we’re still playing.”

For Thornton, which graduates seven seniors, six of them starters, they’ll have to wait until next year.

“We have a lot of good young players,” Petit said. “It’s just going to come down to getting experience and learning the game a little bit more. We’ll be young for a couple years, but we’ll be around.”

— Staff Writer Cameron Dunbar can be contacted at 282-1535, ext. 323 or [email protected].