Roger Federer checked in with Rafael Nadal before going to bed on Tuesday and is relieved the injury suffered by his friend and rival at the Australian Open is not serious.
Nadal had to withdraw from his quarter-final against Marin Cilic in Melbourne due to a leg injury, and, after undergoing scans to determine the extent of the problem, is expected to be back in action next month.
Federer defeated Tomas Berdych in straight sets on Wednesday to book a semi-final against Hyeon Chung, but there will be no repeat of last year's final after the Spaniard's exit.
Speaking in an on-court interview after reaching the last four, the reigning champion revealed he had contacted Nadal to offer his support.
"We wish him well," Federer said. "It's hard to watch someone go out in five sets and not being able to finish. At least if he finishes and loses then all credit to the other guy.
"But Marin deserves an amazing amount of credit, he hung around, it was a massive win for him.
"I wrote to Rafa last night, it was the last thing I did before I went to bed. I had to write to Rafa and see how he's doing.
"I hoped he was going to be okay with the scan today and I am happy the news is not terrible. It was not nice to see, a fellow rival and a friend go out like this."
Chung defeated six-time Australian Open winner Novak Djokovic before dispatching the unheralded Tennys Sandgren, conqueror of Stan Wawrinka, to book a showdown against Federer.
In the absence of the injured Andy Murray, Britain's Kyle Edmund will take on Cilic in the other semi-final.
And Federer has welcomed the presence of some fresh faces in the latter stages of a grand slam.
"I have never played Chung or Edmund and it's great to see new names on the scene," he said.
"We need it, tennis will always create new stars. And the way both made it to the semis is highly impressive.
"For Chung to beat Novak on this court [Rod Laver Arena] is difficult. Apart from that I haven't seen him play very much. I don't play that much. That's my bad!
"He's incredibly impressive in his movement, he reminds me of Novak the way he's able to slide forwards and backwards, use a hard court like a clay court.
"I'm really excited to play against him, he clearly has nothing to lose."
"I'm really excited to play against him. He's clearly got nothing to lose. I will tell myself the same and we'll see what happens."-- #AusOpen (@AustralianOpen) January 24, 2018
- @rogerfederer on his semifinal match-up against @HyeonChung .