Swiss Indoors: Juan Martin del Potro survives Roberto Bautista Agut scare to progress to Basel semis
Del Potro was a distant 47th in the race in late August and his efforts appeared to take their toll on Friday as he suffered a back niggle which required a visit from the trainer.
Basel: Juan Martin del Potro struggled to dominate Roberto Bautista Agut on his way to a 6-2, 2-6, 6-4 win at the Swiss Indoors on Friday as the giant Argentine reached his third successive tour semi-final.
Del Potro, the fourth seed, is fighting for a place in the eight-man ATP Finals in London in just over a fortnight.
He came to Switzerland with a Stockholm title from last week and a Shanghai semi-final boosting his chances.
A third Basel title at the weekend at an event where Roger Federer is looking for his eighth home trophy would send the 29-year-old Del Potro into the eighth and final position for the London showpiece.
He was a distant 47th in the race in late August and his efforts appeared to take their toll on Friday as he suffered a back niggle which required a visit from the trainer.
"I survived, I'm still standing," Del Potro joked. "I've been playing a lot of matches.
"I've had some problems in my body because I've been playing so many matches in a row.
"But I'm not putting my body at risk if I play tomorrow or next week (Paris Bercy). I speak a lot about fitness with my team. There is no risk to keep on playing."
"I will be ready for Saturday, it will be a challenge for me, I'm glad to reach the semi-finals of this event again."
Del Porto, now 17-3 since the start of the US Open, won the first set on Friday but found himself facing a challenge in the second as Spain's Bautista Agut, seeded sixth, broke twice to square the match.
In the deciding third, the Argentine, who beat Federer in the 2012 and 2013 Basel finals, traded service breaks with the Spaniard before winning the seven-miniute penultimate game with a break for 5-4.
Del Potro served out the match to move into a semi-final against either second-seeded defending champion Marin Cilic or Hungarian Marton Fucsovics.
Federer, who underwent two knee surgeries in 2020, and is playing only his third tournament since last year's Australian Open, has always said Wimbledon is his priority this year.
Serena Williams and Roger Federer struggled for form, fitness and matches coming into the French Open. They now approach Wimbledon with a better outlook.
Williams will face Romanian Irina-Camelia Begu on Monday evening under the lights on Court Philippe Chatrier - the scene of her only first-round major exit against Virginie Razzano in 2012.