Juan Martin del Potro defeated Grega Zemlja of Slovenia in straight sets in the final of the €490,000 Erste Bank Open in Vienna on Sunday to put him on the verge of a place at the tour final in London.

Del Potro’s strong serving brought him success in his 7-5, 6-3 victory as he won 82 percent of points on his first serve.

Vienna is del Potro's third title of the year after he won tournaments in Estoril and Marseille.

This triumph all but guarantees the Argentinian one of three remaining places at next month's ATP finals on ranking points as he is 1,020 ahead of ninth-ranked Janko Tipsarevic, with only the top eight to qualify.

Tipsarevic was knocked out in the Vienna semifinal by Zemlja, who reached his first ATP final.

Five players have already secured their places to London including Serbia’s Novak Djokovic, Roger Federer of Switzerland, Britain’s Andy Murray and two Spaniards Rafael Nadal and David Ferrer.