Jeremy Sieverts converted the game-winning goal against St. Paul's with four minutes left in the second quarter.
Then he helped No. 1-ranked McDonogh score a lot more.
Sieverts had three goals and three assists, and Jimmy Daly scored six times in yesterday's 20-5 Maryland Interscholastic Athletic Association A Conference semifinal rout of the defending champions at Homewood Field.
Porter Curran (three goals, one assist), Travis Reed (two, two) and Collins Cary (one, three) contributed for McDonogh (21-1), which won more games this season than in any previously under 13th-year coach Jake Reed.
A championship team in 1999, the Eagles earned a berth in Thursday's title game against No. 2 Boys' Latin, an 11-5 winner over No. 3 Loyola.
McDonogh edged Boys' Latin, 6-5, in overtime in the regular season.
"[Yesterday] we were focused on getting that one more goal, that one more ground ball," said Sieverts, who scored three times in a seven-goal second period that gave McDonogh a 10-1 halftime lead.
"We weren't ready mentally or physically," said 11th-year coach Mitch Whiteley, whose Crusaders routed No. 5 Calvert Hall, 14-4, on Monday. "We might have been tired from Monday, but they were much better."
Midfielder Bryn Holmes (one goal, one assist) had 11 ground balls and won 11 of his first 13 faceoffs and 13 of 19 overall.
"[Last week's] 10-9 loss to Gilman was good for us," Holmes said. "I'd rather lose in the regular season than in the championship."
Defensively, McDonogh All-Metro player Brennan Kelly, Billy Geist and Josh Kahn held second-team All-Metro player Bart Wagner, All-Metro Gavin Gill and Nate Matthews of St. Paul's to three goals and two assists combined.
McDonogh was up 14-1 late in the third quarter.
"Our matchups worked out," Reed said. "St. Paul's didn't have its best game, but we went hard for 48 minutes."
No. 2 Boys' Latin 11, No. 3 Loyola 5: All-Metro player Chris Boland (two goals, four assists), Tad Stanwick (three, two), Brett Weiss (three, one) and goalkeeper Andy Blahut (10 saves) led the Lakers (18-1) to their 10th title game under 26th-year coach Bob Shriver.
"The best two teams are in the championship game," Shriver said.
Loyola (14-3) was led by Steele Stanwick (two goals) and Brady Smith (one goal, one assist). Boys' Latin is pursuing its fifth MIAA crown.