Mauer, a career .359 hitter at Kauffman Stadium, led off the 11th with a double off Jonathan Broxton (1-2) and he scored on Josh Willingham's groundball single to right.
Casey Fien (1-0) worked two perfect innings to pick up his first major-league victory. Glen Perkins worked around Alcides Escobar's leadoff double in the bottom of the inning to pick up his fifth save in eight opportunities.
Greg Holland, the third Kansas City pitcher, worked out of a 10th-inning jam, which Nick Mastroianni led off with a triple to right. Holland stranded him by retiring Alexi Casilla on a grounder with the infield in, then struck out Ben Revere and Jamey Carroll. Holland struck out four in two innings.