John Grubb hit two homers and Alan Trammell went three for five with three RBI as the Detroit Tigers defeated the fading Blue Jays, 10-4, yesterday in Toronto.

The Tigers reduced their magic number for clinching the American League East title to 11, while increasing their lead over the second-place Blue Jays to 10 1/2 games.

Bill Scherrer (1-0), in relief of Jack Morris, pitched 1 2/3 shutout innings and struck out three. Morris, making his third unsuccessful bid to become the league's first 18-game winner, left with one out in the fourth, feeling stiffness in his right shoulder.

Aurelio Lopez worked three innings to earn his 13th save. In the ninth, he permitted RBI singles by Dave Collins and Willie Upshaw.

The Tigers' manager, Sparky Anderson, said, "I don't have to be very smart to call down to the bullpen and ask for guys like Lopez and Willie Hernandez. All it takes is an IQ of 3. It's a lot more difficult when you call down and have to say 'Give me . . . umm . . ."

Detroit broke a 2-2 tie with two runs in the seventh. Grubb hit a 1-2 pitch from Luis Leal (13-6) over the right field fence, Lou Whitaker singled and, after a wild pitch, Trammell doubled a run in.

Detroit put the game away with six runs in the eighth.