Emma Raducanu was forced off court during her Queen's Club quarter-final against Kamilla Rakhimova after a worrying fall brought play to a halt.
The British star had been in control of the contest, taking the opening set and moving a break ahead in the second, when she slipped during the opening point of the fifth game.
After returning Rakhimova's serve, Raducanu was wrong-footed by her opponent and tumbled heavily to the court, immediately sparking concern among those watching.
BBC commentator Annabel Croft reacted in alarm as the former US Open champion stayed down.
"Oh, ouch!" Croft exclaimed. "Oh, dear. Oh, no. Let's hope she's alright. She might need a minute here."
"It's always such a shock going down, because you don't know what you've done until you get back up again. And then, worse than that, it makes you worry about what's going to happen again when you get a wrong-footer."
Raducanu eventually got back to her feet and continued, but the concern did not subside.
Rakhimova went on to win the game before Raducanu requested further treatment, prompting the Brit to call for medical assistance.
The chair umpire then informed the crowd: "Ladies and gentlemen, Raducanu will be receiving a medical timeout off court."
The announcement meant play would be suspended for at least three minutes while the 23-year-old received treatment away from the court.
Raducanu disappeared down the tunnel alongside the physio, leaving her opponent waiting on court as spectators anxiously awaited an update.
As the delay stretched beyond five minutes, BBC commentators noted their surprise that no further announcement had been made, with Rakhimova left waiting for an extended period before play could resume, keeping herself warm with a series of unopposed serves.
There was relief for the home crowd when Raducanu eventually emerged from the tunnel and made her way back onto court.
However, the extent of the issue appeared clear as she returned with heavy strapping on her left thigh before attempting to continue her bid for a place in the Queen's final.
The injury scare came at a crucial stage of the match, with Raducanu holding both the momentum and a lead in the second set as she looked to book her place in the showpiece event.
