MIAMI GARDENS, Fla. >> Despite a change in venue, the Miami Open has a familiar look, with John Isner back in the final.

The defending champion moved closer to another title by hitting 21 aces today and defeating 18-year-old Canadian qualifier Felix Auger-Aliassime 7-6 (3), 7-6 (4).

Next is a Sunday showdown in the Miami Dolphins’ stadium, where the tournament moved this year from its longtime home of Key Biscayne.

“The venue is absolutely fantastic,” said Isner, a big football fan. “To play in the stadium — the Super Bowl will be here next year — it’s pretty amazing.”

Isner’s opponent in the final will be the winner of today’s match between three-time champion Roger Federer and another Canadian teenager, 19-year-old Denis Shapovalov. Now 33, Isner won his only ATP Masters title a year ago on Key Biscayne.

“It’s amazing,” Isner told the crowd after his latest win. “I said before the tournament the chances were I would not defend my title. I’m very, very happy.”

The women’s final Saturday will match No. 5 Karolina Pliskova of the Czech Republic against No. 12 Ashleigh Barty of Australia.

Auger-Aliassime served for both sets in the semifinal, but Isner broke each time by taking advantage of double-faults, and then used his big serve to control the tiebreakers.

Nine of his 10 sets in the tournament have gone to a tiebreaker, and he has won each one. But Auger-Aliassime figured neither set should have gotten to that point.

“It’s a chance you can’t miss, serving two times for the set,” he said. “Just terrible.”

Auger-Aliassime, 5-0 previously against top 20 opponents, was the youngest male semifinalist in the tournament’s 35-year history. He’ll jump to a career-best No. 33 in next week’s rankings.

But he’ll need steadier play at pivotal moments to fulfill his potential as a future Grand Slam champion.

Isner lost serve for only the third time in the tournament to fall behind early. Auger-Aliassime served at 5-4 but double-faulted into the net three times, including on break point.

There was a repeat in the second set. Auger-Aliassime served at 5-3, double-faulted once and then hit a swinging volley into the net on break point.

The teenager blamed nerves.

“It’s like I caught a virus or something,” he said. “I couldn’t put a second serve in anymore. That’s just very tough to swallow.”

Each lapse led to a tiebreaker, where Isner has been unbeatable of late after arriving at Miami with a modest 7-10 record in tiebreakers this year.

He finished strong against Auger-Aliassime, whacking three aces in the final tiebreaker, the last on a 140 mph serve that was his fastest of the match.

“I’m playing well,” Isner said. “Keep it up and see what happens.”