After the disappointing finish to Indian Wells and a missed chance at 101 and No. 28 on the Masters circuit, you just know Federer is not going to want to blow a second chance in a big final against a non-Big 4.
Tsitsipas, 20, shocked Federer in the fourth round of the Australian Open and was runner-up to Federer in February in Dubai, where the Swiss great claimed his 100th career ATP title. In the quarters, he defeated Roberto Bautista Agut following which, he dispatched the Canadian qualifier Felix Auger-Aliassime.
The 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.
The Canadian got his opening break in the seventh game of the first set and went ahead 4-3 before then holding serve.
The 19-year-old came out stronger for the second set and, after holding serve, looked to be on his way to breaking Federer for the first time.
Federer netted a forehand right after serving in the seventh game to push Agassi 4-3 up, with the American cementing the break after deuce before sealing the deal with a backhand down the line victor in game nine for the second break and a 6-3 after 35 minutes.
"What a week its been for me", said the fourth seed.
"I will try and approach it like any other game, try and enjoy it, give it my all".
Federer said he felt badly for Isner but didn't let that affect his game.
Isner began to get his serve going in the second set, holding his first four serves.
Yet it didn't settle him down and when another horribly loose backhand flew long, Federer pocketed a vital early break for 2-1.
Shapovalov, meanwhile, needed to mount a comeback after losing the first set to Tiafoe in a tiebreak.
"For sure (it was) nerves", said Auger-Aliassime, the youngest men's semi-finalist in the tournament's 35-year history. And the Canadian held to start the second. "I'm happy I was able to play with variations".
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The towering 6-foot-10 Isner overpowered Auger-Aliassime in the second tie breaker to win the match, hammering three consecutive aces, with the last one clocked at a match-high 140 miles per hour.
"It was just important to keep on doing what I was doing, and if he's hurt, well, then so be it, and bad luck for him", Federer said.