Nishikori beats Del Potro for the first time

Kei Nishikori secured his first ever victory over Juan Martin del Potro in the quarter-finals of the Swiss Indoors Basel on Friday.

The Japanese World No 5 had lost all four of his previous matches against the powerful Argentine, but his 7-5, 6-4 victory on this occasion was a testament to his newfound status in the men's game.

Del Potro had been in solid form heading into the match, and there wasn't that much separating the two players, but Nishikori was able to win the points that mattered, ultimately wrapping up a straight sets wins courtesy of a solitary break of serve in each set.

Nishikori has now won 55 ATP World Tour matches this season – more than any other player on tour.

He will look to reach his fifth final of the year on Saturday when he takes on Gilles Muller, who needed nearly three hours to get past Federico Delbonis 6-7 (4-7), 6-4, 7-6 (7-3).

It was a remarkable comeback from Muller, who was staring down defeat with Delbonis serving for the match at 5-3 in the second set.

The man from Luxembourg is also experiencing his most successful season on the ATP Tour, having won a career-high 34 matches this year.

Mischa Zverev

There was a big upset later in the day as top seed and home favourite Stan Wawrinka was beaten 6-2, 5-7, 6-2 by Germany's Mischa Zverev.

Zverev – ranked just 72nd in the world – stunned the Basel crowd by taking the first set against the US Open champion, and though Wawrinka was able to hit back in the second and level the scores, Zverev would utterly dominate in the third set, claiming three successive breaks to wrap up the big win.

He moves on to face the winner of the match between Marin Cilic and Marcel Granollers-Pujol.