BASEL, Switzerland (Reuters) – Juan Martin del Potro’s quest for an unlikely spot in the ATP World Tour Finals gathered pace as he beat Portugal’s Joao Sousa in his opening match at the Swiss Indoors on Wednesday.

The Argentine, twice champion in Basel, maintained the form he showed last week in capturing his first title of the year in Stockholm by overpowering Sousa 6-1 4-6 6-1.

Fourth seed Del Potro will face French qualifier Julien Benneteau in the last 16 at the St Jakobs Hall, where hometown favorite Roger Federer is bidding for an eighth title.

It looked being a quick assignment for the former U.S. Open champion as he blazed away with his power game but a lapse at 4-4 in the second set allowed Sousa to break and level.

But Del Potro stamped his authority on the decider.

“I need to improve my game a little bit for tomorrow and see if I can keep winning because I’d like to spend more days in Basel,” the fourth seed said.

Del Potro began the tournament 14th on the ATP Race to London list but with several players above him missing the rest of the season, the door is still open for the 29-year-old to sneak into the prestigious year-ender in London.

Should he win the title in Basel he would be breathing down the neck of Spain’s Pablo Carreno Busta, currently holding the last of the eight spots heading into next week’s Paris Masters.

Six places have already been taken, but Belgium’s David Goffin is also in the mix after beating South Korea’s Chung Hyeon 6-4 6-1 to move into the third round in Basel.

American Sam Querrey and South Africa’s Kevin Anderson are also in with a chance of making London as is France’s Jo-Wilfried Tsonga.

Croatian youngster Borna Coric set up a meeting with second-seeded compatriot Marin Cilic when he came back from squandering set points in the opener to beat Swiss Henri Laaksonen 6-7(8) 6-1 6-3 in one of the day’s other first-round matches.

Top seed Federer, bidding to catch Rafa Nadal and finish a resurgent year as number one in the rankings, returns to action on Thursday when he takes on Frenchman Benoit Paire.