MIAMI GARDENS, Fla. — 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.
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.
''It's amazing,'' the 33-year-old Isner told the crowd after his victory. ''I said before the tournament the chances were I would not defend my title. I'm very, very happy.''
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.