John Isner, who hit 21 aces against Felix Auger-Aliassime, has won 11 matches in a row at the Miami Open
Defending champion John Isner reached another Miami Open final by ending Canadian teenager Felix Auger-Aliassime's historic run.
The 33-year-old American edged out his 18-year-old opponent, who was playing in his first Masters semi-final, in a 7-6 (7-3) 7-6 (7-4) victory.
Auger-Aliassime was left to rue missed chances, failing to serve out at 5-3 in the first set and 5-4 in the second.
Isner fought back to edge both sets and could face Roger Federer in the final.
Switzerland's 20-time Grand Slam champion Federer, 37, takes on Denis Shapovalov - another Canadian teenager - in the other semi-final later on Friday.
Auger-Aliassime, aged 18 and 233 days, is the youngest man in the tournament's 35-year history to reach the last four, having beaten a 14-year record set by Spanish 17-time major winner Rafael Nadal.
Despite the inevitable frustrations of not taking his chances against Isner, the Canadian qualifier will reflect positively on a remarkable week that has announced his arrival as one of the sport's brightest young talents.
His performances in Florida mean he will be the first male player born in the 2000s to reach the world's top 50, climbing up to 33rd when the rankings are released on Monday.
"Felix can get to the very top," Isner, who has won nine of his 10 sets in Miami in tie-breaks, said.
"I can't say enough good things about him. He has got it all. He is very humble and won't let success get to him."
Felix Auger-Aliassime received a standing ovation as he made his way off court after losing to Isner
