Passeau's greatest individual performance came in Game 3 of the 1945 World Series, in which he pitched a one-hitter against the Detroit Tigers. Slugger Rudy York got the Tigers' only hit, in the second inning, and the Cubs took a 2-games-to-1 edge. Due to wartime travel restrictions that were still in place, despite the war having ended, the first three games were in Detroit and the last four in Chicago. Back in Wrigley Field, the Cubs lost three of four games, their last appearance in the Series until 2016. Passeau was the starting pitcher for the Cubs in Game 6, but had to be removed from the game during the sixth inning after he injured his pitching hand while fielding a hard smash. Passeau had a comfortable lead in the game, but the Chicago bullpen could not check the Tigers. The game went into extra innings and the Cubs emptied their bench. Hank Borowy, who was scheduled to pitch Game 7, was pressed into service and pitched four innings as Chicago won the game in twelve innings. Passeau's injury proved to be costly as the Cubs were without a well rested pitcher to face Hal Newhouser in the final game.