Federer stressed that keeping up to speed with the Spaniard is dependent on the type of surface, and the need to not take any shot for granted.
“I mean, obviously it’s surface-based,” Federer told Athlon Sports.
“Not every surface allows you just to power through. Maybe against Alcaraz, sometimes you have to outmanoeuvre him, which is obviously super difficult.
“What I did see is just what he’s able to cover, and with the speed that he has, you have to go in with a mindset that you need to win the point twice.”
Best bits: Alcaraz wows New York to beat Sinner and claim second US Open title
Video credit: TNT Sports
When addressing Alcaraz’s athleticism on the court in more detail, Federer added: “That can really throw some question marks.
“Even if you’re hitting an easy forehand that’s normally a winner.
“Now, you don’t know if it’s going to be a winner or if you’ll need an overhead smash. So, you always have an extra chance to miss a ball.”
The 22-year-old has shown a few chinks in his armour though, losing to Taylor Fritz at the Laver Cup, giving hope to the rest of the ATP Tour.
Fritz’s victory proved vital in securing a 15-9 win for Team World, as he defeated Alcaraz 6-3 6-2 in a fine display by the American.
Fritz stuns world No. 1 Alcaraz in Laver Cup
Video credit: SNTV
Federer reviewed that match in more detail, praising Fritz for brilliantly utilising the fast indoor court conditions in San Francisco.
“I would obviously play very aggressive against him on an indoor court like this, like Taylor did – keep coming at him, make him feel uncomfortable, mix it up, come in some,” he explained.
“I thought that Taylor did an amazing job, serving clutch when he had to, and then just being really solid when he did.
“And also, in defence, you have to show the whole arsenal against Carlos, because he will stress that out and figure it out normally.”
That result was the only blemish in what has been an incredible run of form from Alcaraz in recent months, with that his only defeat in 18 previous matches.
That victory means Alcaraz equalled his career-high season win record with 65, as he prepares to face Casper Ruud in the last four.
This will be Alcaraz’s ninth successive semi-final on the tour, and believes this is the finest spell of form in his career.
He said: “Probably [it’s the best period of my career]. I’m just feeling great on court, every time I step on the court.
“I just think I can do everything. I’m approaching the end of the season with a lot of confidence and these kinds of matches, this kind of level, helps a lot to keep the confidence high.
“I’m just trying to set up goals before matches, before tournaments, and trying to follow those goals. I think that helps me a lot to play great tennis and maintain the focus during the match.”
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