And that's not all. With Cohasset down 22-3 after O'Leary ran in his second touchdown, the Skippers scored on an 8-yard pass to trim St. Mary's lead to 11 points with 1:28 left in the game. Cohasset, in need of a miracle, attempted an onside kick, hoping to regain possession. But O'Leary recovered the ball to seal the deal.
"Derek shows up everywhere and he does it quietly," first-year St. Mary's coach Sean Driscoll said. "He had two touchdowns running the ball. That's a good thing."
The Spartans advanced to the Division 7 state championship game. They'll battle Blackstone Valley at Gillette Stadium (TBA).
"It feels great," said O'Leary, a junior and first-year starter under center. "I can't believe we're here. It's unbelievable."
O'Leary finished 3 for 3 with 75 passing yards.
"I'm ready to throw the ball," O'Leary said. "Running the ball a lot brings the safeties and the defensive backs up. It just makes my job easier."
Driscoll said he came away impressed with O'Leary's performance.
"He made three top, accurate throws," Driscoll said. "Exactly what we asked him to do and wanted him to do, he does. That's why he's been our quarterback all year. He doesn't do anything to hurt us and he knows what we're looking for. That's a big thing with him and I'm very proud of him for that."
O'Leary completed two passes to receiver Eni Falayi for 50 yards and one to Jalen Echevarria for 25 yards. Echevarria's catch came during a critical fourth-and-15 scenario in which the Spartans were clinging to an 8-3 lead in the fourth quarter. O'Leary finished that drive with a 2-yard keeper.
"It's awesome to have a 6-5 target like Eni," O'Leary said. "Jalen plays basketball. He can go up and get any throw I make.
"We came out and did what we had to do. Everybody played great, especially the guys that got hurt during the game. They stuck through it and helped us get the win."
O'Leary added a 1-yard keeper to close the scoring for St. Mary's, giving the Spartans a 22-3 lead with 3:34 to play. The Skippers found the end zone on an 8-yard touchdown pass.
"It was a great game for us," Driscoll said. "It was really a great team effort. Now we'll go from there."
St. Mary's visits rival Bishop Fenwick Thanksgiving morning (10) at Donaldson Stadium for the Catholic Central League title before shifting gears to the state championship game.