By Ricky Dimon

 

Pablo Carreno Busta, Sam Querrey, and Kevin Anderson are leaving the door to the World Tour Finals wide open. Juan Martin Del Potro and Jo-Wilfried Tsonga are still walking through it.

Coming off respective titles in Stockholm and Antwerp, Del Potro and Tsonga maintained their fine form with quarterfinal victories on Friday. Del Potro held off Roberto Bautista 6-2, 2-6, 6-4 to reach the semis of the Swiss Indoors Basel, while Tsonga upset Alexander Zverev 7-6(6), 6-2 for place in the last four at the Erste Bank Open.

The 19th-ranked Argentine, whose recent hot streak also includes semifinal performances at the U.S. Open and the Shanghai Masters, needed two hours and one minute to hold off Bautista Agut. Apparently hobbled by a minor back issue, Del Potro gave back a break midway through the third set but broke again at 4-4 before serving it out.

“It was a really hard match,” the 2009 U.S. Open champion assessed. “Bautista played some unbelievable shots the whole match. We played at a great level and I survived and I’m still alive to qualify for London. I know I am getting closer and closer to qualifying, but I need to keep winning here and in Paris. We’ll then see if I qualify or not.”

 

Del Potro has gotten help this week from Carreno Busta, Querrey, and Anderson, who remain ahead of him in the race for the final two spots. Querrey and Anderson lost in the Vienna first round, while Carreno Busta fell in the Vienna second round to Diego Schwartzman.

 

Tsonga still has a chance of advancing to the title match out of Carreno Busta’s half of the draw. The 15th-ranked Frenchman ousted the top-seeded Zverev in one hour and 32 minutes, striking 10 aces while also benefiting from seven double-faults by Zverev.

 

In order to qualify for the World Tour Finals, Tsonga likely has to win the Vienna title and also make a deep run at next week’s Paris Masters. If Tsonga fails to lift the Vienna trophy, he will have to reach the Paris final at the very least.

 

Next up for the No. 8 seed is Philipp Kohlschreiber, who defeated Schwartzman 7-5, 7-6(6). Del Potro will meet Marin Cilic, a 7-6(3), 5-7, 7-6(4) winner over Marton Fucsovics.

Ricky contributes to 10sballs.com and also maintains his own tennis website, The Grandstand. You can follow him on twitter at @Dimonator.