Three days before the Rolex Paris Masters, with a place at the Nitto ATP Finals still to secure, Arthur Fils walked off court in Basel holding his lower back. The Frenchman, seed No. 2, retired trailing American Taylor Fritz 6-2, 2-0 on Friday evening, sending the No. 6 seed into the semifinals of the Swiss Indoors Basel, where he will face Valentin Vacherot of Monaco.

The timing is the worst part. Fils sits inside the qualifying places in the Race to Turin with 3,525 points, 545 clear of Alex de Minaur, the first player outside them. Paris, which starts on Monday at the Paris La Défense Arena in Nanterre and offers 1,000 points to its champion, was supposed to be where he made his place safe. Now his presence there depends on his back. It is an area that had already troubled him repeatedly since May 2025.

The problem surfaced at 2-5 in the first set. Fils called the physio at the changeover, pointed to his lower back and left the court with a towel over his shoulders for three minutes of treatment. He came back, lost the set 6-2 on Fritz’s serve, then dropped his serve in the opening game of the second set. At 2-0 down, he told the umpire he could not continue. It looked like a decision taken to protect his chances in Paris.

Before the treatment, Fils had been short of energy, cutting rallies as short as he could while the crowd tried to lift him with cries of “Allez Arthur!” The first set was a scrappy affair, with unforced errors piling up on both sides and too few winners to make up for them. Fritz broke three times, against once for Fils.

For Fritz, the result keeps a longer shot at Turin alive. The American moves to 2,885 points in the Race, 324 behind Rafael Jodar, who holds the eighth and last qualifying spot, with a final in Basel and Paris still to play for. His retirement win also means Jodar’s Top 10 debut on Monday is no longer guaranteed; a Fils win would have secured it.

Ranked No. 13, Fritz turned 29 on Wednesday. He reaches his first semifinal in Basel, and his fourth in five ATP 500 events this season after Dallas, Halle and Washington. The win is his 40th of the season, the fifth consecutive year he has reached that mark, and it levels his head-to-head with Fils at 1-1. The Frenchman had won their first meeting 6-4, 3-6, 6-3 in Tokyo in 2024.

Fritz had beaten Australian lucky loser Rinky Hijikata 6-4, 7-6 (3) and Canadian Denis Shapovalov 6-4, 6-3 earlier in the week. Fils, 22, had edged out qualifier Giovanni Mpetshi Perricard 7-6 (5), 7-5 and American Alex Michelsen 4-6, 6-3, 7-6 (5).

Vacherot reached the semifinals by beating Holger Rune 6-3, 3-6, 6-3 on Friday afternoon.