Oswego (28-12) will face top-seeded UMass Boston at 4:30 p.m. on Saturday at Massachusetts Maritime Academy in Buzzards Bay, Mass. The games on Saturday were moved to a facility with a turf field in anticipation of rain.
Donnelly and Keystone's Dakota McFadden matched zeros for the first four innings as Donnelly permitted just one batter to reach scoring position over the stretch.
The Lakers took advantage of McFadden's control lapses in the fifth as senior Eli Holton drew a free pass to start things off. Keystone's hurler then struck out the next two batters, but senior Zach Whelan ripped a single to right to plate Holton.
The late innings moved quickly, with the Knights putting two runners on with one out in the seventh, but Donnelly bore down for two groundouts to end the threat.
Oswego added a run in a miscue-ridden eighth, with junior Brandon Nicholson drawing a hit-by-pitch and moving to second on a failed pickoff attempt that sailed into right field. Nicholson then came around to score on a botched groundball at first base.
Donnelly came out for the ninth and – after a quick out – gave up a live drive up-the-middle to Keystone. The right-hander, however, then induced a bouncing ball that Whelan handled with a dive just to the left of second, quickly tossed underhand to Nicholson, who barehanded the ball and fired a missile to first base for the game-ending double play.
Donnelly (6-3) fanned six batters on strikes while senior Kevin Hylas was the lone multi-hitter in the contest as he went 2-for-3 while adding a stolen base.