American 11th seed John Isner’s hopes of surpassing his best finish at a US Open could be cut short if his first baby arrives sooner than expected.

Isner reached the quarter-finals with a 3-6 6-3 6-4 3-6 6-2 win over Canadian 25th seed Milos Raonic on Sunday to equal his best showing here.

His first child is due on 22 September but he has already been thinking what would happen if there was a clash.

“I would play if it worked out I could get there and get back,” he said.

He added in comments reported on the US Open website: “If it was the day of the match, not possible. I’m not going to miss the birth, but we’ll see.”

Wimbledon semi-finalist Isner will face Juan Martin del Potro or Borna Coric next after reaching the last eight in New York for the first time since 2011.

He is the only American remaining in the men’s draw after 18th seed Jack Sock was knocked out by Georgian Nikoloz Basilashvili in the second round.

• Defending champion Nadal through
• Murray into mixed doubles quarter-finals
• Djokovic and Federer seeking last eight tie

Elsewhere, ninth seed Dominic Thiem also reached the quarter-finals by beating 2017 runner-up Kevin Anderson 7-5 6-2 7-6 (7-2) of South Africa.

The Austrian broke late in the first set and twice in the second before winning the third in a tie-break on Arthur Ashe Stadium..

It is the first time Thiem has reached the last eight in New York, and he will face 17-time Grand Slam winner and defending champion Rafael Nadal.

French Open finalist Thiem called the win “one of his best matches ever”.

Twelve months ago the 24-year-old had two match points in the fourth round against Del Potro but lost in five sets.

“It’s a dream coming true,” said Thiem. “I was really close last year, but I couldn’t close it out.”

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