Defending champion John Isner earned a return trip to the Miami Open final by hitting 21 aces and defeating 18-year-old Canadian qualifier Felix Auger-Aliassime 7-6 (3), 7-6 (4) on Friday.
The 33-year-old Isner won his only ATP Masters title a year ago. His opponent Sunday will be the winner of the second semifinal between three-time champion Roger Federer and another Canadian teenager, 19-year-old Denis Shapovalov.
Auger-Aliassime served for both sets, but Isner broke each time by taking advantage of double-faults, and used his big serve to control the tiebreakers. Nine of the 10 sets Isner has played in the tournament have gone to a tiebreaker, and he has won each one.
Auger-Aliassime was the youngest male semifinalist in the tournament’s 35-year history.