Unseeded Russian Karen Khachanov advances to US Open semifinals after hobbled No. 28 seed Alexander Blockx retires in third set

Alexander Blockx tried to give it a go but the 28th-seeded Belgian was too hobbled to finish Wednesday with a trip to the US Open semifinals at stake at Arthur Ashe Stadium.

Blockx retired in the third set against unseeded Russian Karen Khachanov while trailing 6-2, 7-5, 3-2, unable to continue with a rib injury that had hobbled him since the Round of 16. The injury bothered Blockx throughout the match.

He visibly struggled with his serve in the first set, where he was broken twice. He took a medical timeout between sets to have work done not on his ribs, but his left foot.

He stayed in the match and remained on serve in the second set until Khachanov broke him late to serve for the set, 7-5. Blockx then took another medical timeout, this time to have work done on his torso.

He was in pain in the third set and opted to retire when Khachanov broke him again to take a 3-2 lead. He informed the chair umpire of his decision, then shared an embrace with Khachanov.

Khachanov, 30, advances to face the winner of Wednesday's prime-time match between No. 1 seed Alexander Zverev and unseeded Botic Van De Zandschulp.

Khachanov back in semis despite downturn

The trip to the semifinals marks the second for Khachanov at the US Open. He lost as the No. 27 seed in the semifinals in 2022 to No. 5 seed Casper Ruud, who went on to lose to Carlos Alcaraz in the championship match. It's the third trip to a Grand Slam semifinal and his first since advancing to the Australian Open semis in 2023.

Khachanov willl play in the semifinals ranked 50th in the world, his lowest ranking since 2017. He spoked about the conflicted feelings of defeating an injured opponent in his post-match interview.

"It's a mixed feeling," Khachanov said. "From one side, I was feeling I was dominating from the beginning. Then I started to feel like he was struggling more and more. …

"He's suffering, I don't want to scream 'come on' or something like that. I wanted to keep the energy still there. I wish him a speedy recovery, definitely. … I'm super happy. I'm in the semifinals; come on."

Blockx's run to the quarterfinals was his deepest ever at a Grand Slam and the deepest ever by a Belgian at the US Open. He got there by upsetting No. 5 seed Flavio Cobolli in the third round, then beating No. 24 seed Francisco Cerundolo on Monday in the Round of 16.

He defeated Cerundolo while playing through pain. He told reporters after that match that medication did little to relieve his pain during play.

"I was just hanging in there," he said. "If I would have lost the third set, the chances would have been really high of me retiring."

On Wednesday, the pain alongside a steep deficit to Khachanov proved to be too much to play on.