Young US Open star Carlos Alcaraz was forced to retire midway through the second set of his quarter-final against Felix Auger-Aliassime on Tuesday.
The physical toll of the Spaniard’s headline-grabbing Grand Slam run ultimately proved too much to sustain, with Alcaraz throwing in the towel at 3-1 down in the second after losing the opening set 6-3.
Alcaraz had beaten both Stefanos Tsitsipas and Peter Gojowczyk in five-set epics to reach his first Grand Slam quarter-final, and the impact of those lengthy matches on the 18-year-old’s game was clear from the off.
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The youngster made 16 unforced errors in the shortened encounter, with his now trademark booming groundstrokes falling well short of their previous standard.
And, to his credit, Auger-Aliassime kept his composure to take advantage of his opponent’s lacklustre display to put himself in control of the match before the trainer was called during the first changeover of the second set.
“It’s really tough to end a great tournament like this. I had no choice to still play,” Alcaraz said after the match.
“First of all I have to take care of my body to stay healthy. It’s a long match and I didn't feel good to still play, so I had to retire.
To play two fifth sets in a row, play on a great level, in a great intensity for four hours, it was really tough for me. I am not used to playing these kind of matches in a row. I think it was really tough to recover for the next matches.
“These matches gave me a lot of experience, so I think this tournament made me mature a lot. I think I played great tennis for me,” Alcaraz added.
“I’m really happy to play a first quarter-final in a Grand Slam. I think this is going to be a great experience for me for the next tournaments.”
Victory for Auger-Aliassime sees him reach the last four of a tennis major for the first time in the 21-year-old blossoming career, bettering his previous career best of a quarter-final appearance at Wimbledon earlier this summer.
The Canadian will face Daniil Medvedev in the last four.

Félix Auger-Aliassime.

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Earlier in the day Medvedev dropped his first set of the tournament, but advanced to the semis with a 6-3 6-0 4-6 7-5 win over Botic van de Zandschulp.
The Russian number two seed breezed into the quarter finals without dropping a set. That perfect run came to a halt as Van de Zandschulp took the third set, but it proved to be a minor blip as he rallied to dispose of his opponent in two hours and 22 minutes.
Van de Zandschulp showed flashes of quality, but they were not enough against a player viewed as the biggest obstacle to Djokovic completing the calendar Grand Slam.

Daniil Medvedev of Russia

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Medvedev raced out of the blocks, and an opening break of serve put the world number 117 on the back foot.
The Russian’s clean hitting from the baseline overwhelmed Van de Zandschulp early on, and it came as a surprise when the Dutchman worked a break point in the eighth game.
He earned it following a punishing rally, and one shot later Medvedev dumped a backhand slice into the net.
Van de Zandschulp played a couple of glorious passing shots in the following game, but Medvedev steeled himself to break back and wrap up the opening set.
The underdog won a four-hour, 20-minute epic against Diego Schwartzman in the previous round and those efforts appeared to take a toll as his movement began to falter.

Van de Zandschulp.

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After Medvedev raced through the second set to love, Van de Zandschulp called on the trainer for treatment on his legs.
The trainer's magic hands did their job as Van de Zandschulp came out swinging at the start of the third set. He broke serve and took advantage of a drop in level from Medvedev to take the set.
There were 13 unforced errors from Medvedev in the third set, and Van de Zandschulp took confidence from being able to worry the Russian.
The fourth set became a battle, but Medvedev limited the errors and he eventually secured the telling break in the 12th game to wrap up the win.
Medvedev's serve was extremely solid in the fourth set, and the quick service games piled pressure on Van de Zandschulp.
The Dutchman staved off a match point in the 10th game, but two games later the Russian took advantage of a double fault to book his place in the last four.
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