Everything seemed to be progressing perfectly for Emma Raducanu in the early stages of a day that, in the best case scenario, would require a marathon effort like no other. The British No 1 was in the middle of putting together a cool, efficient performance on a mercifully sunny day in Barons Court. She led, 6-3, 3-1.

Then she slipped on the slick grass. Raducanu emerged from her fall wincing and clutching her left thigh, clearly in pain, and as her lead evaporated, a victory began to look in serious doubt. However, Raducanu impressively dug deep and held her nerve to drag herself into the semi-finals at the Queen’s Club for the first time with a 6-3, 7-5 win over the Uzbekistani lucky loser Kamilla Rakhimova.

The injury, however, leaves Raducanu with serious questions for her semi-final against the 18-year-old Iva Jovic, the sixth seed and world No 19, which is scheduled to be played later on Saturday.

Asked about how her thigh felt , Raducanu said: “I think it’s a mix of adrenaline, but it was tough to take that fall. I felt like I was in a pretty good spot in the match. On grass, these things happen. I found it pretty tough to regroup, but I’m really proud of how I did that with the help of [the home crowd].”

Raducanu had comfortably closed out her best victory for more than a year on Friday, serving well and playing decisive, offensive tennis to defeat the world No 18 Sorana Cirstea in straight sets. Their match had been postponed from Thursday after rain had led to the cancellation of the entire day, meaning all second round winners were scheduled to play twice on Friday.

Less than 24 hours after registering the biggest victory of her career, defeating the world No 2, Elena Rybakina, in a dramatic three-set match, Katie Boulter had little energy left for a tough semi-final against the lucky loser Donna Vekic. Boulter fell quickly, losing 6-1, 6-3 to the veteran Croat.

Boulter struggled from the beginning in an error-strewn opening set, her poor serving setting the tone for a difficult day. She landed just 47% of first serves in the opening set and her second serve was dismantled throughout. Although Vekic is ranked No 76, she is an accomplished player who thrives on grass. A Wimbledon semi-finalist in 2024, she reached a career-high ranking of No 17 last year. Now she will compete for her biggest title.

This was a winnable match for Boulter and an opportunity missed, but her immense effort on Friday, when she won two matches, played five sets and finished in the evening, clearly left its mark. As a result of this great start to her grass season, she will return to the top 60 and tackle the rest of this swing full of confidence in her game and ability to beat the best.

Raducanu initially appeared to be easing to victory when she slipped on the grass after being wrong-footed at the beginning of Rakhimova’s service game while leading 6-3, 3-1. The slip was not as bad as Victoria Mboko’s horrible fall earlier in the week, which led to her immediate retirement and a swift withdrawal from Wimbledon due to a torn medial collateral ligament, but Raducanu took a while to rise from the ground and she was holding her inner thigh when she did.

She did not move much for the remainder of the game and after walking gingerly back to her chair, Raducanu asked for the trainer and received an off-court medical time out. She returned with her left thigh taped and the complexion of the match had completely changed. She immediately found herself 0-40 down in her service game. Before long, she had lost three consecutive games to trail 3-4 in set two.

Aside from some last-ditch offensive play when Raducanu first served for the match at 5-4, Rakhimova did little to exploit her opponent’s obvious uncertainty and discomfort with her movement, resorting to just putting the ball in court and waiting for Raducanu to miss. Raducanu was clearly rattled mentally, but once she focused and forced herself back on the front foot, she willed herself to victory.

This is quite a noteworthy occasion for Raducanu, a fifth tour level semi-final since her US Open title run in 2021 and her second at WTA 500 level or above. Six months into an extremely difficult year, filled with various physical ailments and absences, she finally looks comfortable and confident.

This should be a moment to reflect on a positive step forward at last, but instead Raducanu’s thoughts will again be focused on trying to ensure that her body is in good enough shape to be competitive against one of the best players in the world.