Kei Nishikori ended Juan Martin del Potro’s long winning run at the Swiss Indoors, edging their quarterfinal 7-5, 6-4 on Friday.
Top-seeded Stan Wawrinka’s long underachieving run in Basel continued when the US Open champion lost 6-2, 5-7, 6-1 to 72nd-ranked qualifier Mischa Zverev of Germany.
In 13 editions of his home country’s top event, Switzerland’s No. 1 Wawrinka has never reached the final and had not won a match in four straight years before coming through two tight three-setters this week.
Nishikori, the world No. 5, is now the highest-ranked player left in a tournament where he lost the final to Roger Federer in 2011.
The third-seeded Japanese saved all eight of Del Potro’s break-point chances, and created match point with his seventh ace. Nishikori clinched with an overhead volley winner at the net.
“I saved a lot of important points with my serve,” said Nishikori, who had 10 break chances and took one in each set. “I played good tactics today.”
Del Potro won back-to-back Basel titles in 2012 and 2013 – beating hometown favorite Roger Federer both times – then missed the next two editions due to persistent left wrist injuries.
The 28-year-old Argentine took a wild-card entry here as he steadily climbs the rankings again. He is poised to rise from No. 42 in the new list published on Monday.
No. 3 Wawrinka completed a family double having been beaten by Zverev’s teenage brother, Alexander, two weeks ago in the final at St. Petersburg, Russia.
Wawrinka, whose serve was broken in the opening game, seemed to have winning momentum when holding a break point to lead 2-0 in the deciding set.
Zverev held serve and, during a run of six straight games to seal victory, provoked Wawrinka to smash his racket to the ground.
In Saturday’s semifinals, the 29-year-old German left-hander will play fourth-seeded Marin Cilic of Croatia who got the better of Marcel Granollers of Spain by a 6-3, 6-3 scoreline.
Nishikori is seeking his second title of the season and to reach his fifth final. He also won on indoor hard courts at Memphis in February.
He plays Gilles Muller of Luxembourg, who earlier outlasted Federico Delbonis of Argentina 6-7 (4), 6-4, 7-6 (3).
Muller clinched the 2-hour, 45-minute match with five straight points in the third-set tiebreaker soon after Delbonis served for victory at 5-3.