Uzbek Denis Istomin beat Argentinian Horacio Zeballos 7-5 7-6 (7-3) on Tuesday to book a second round meeting with former world No.1 Roger Federer at the Swiss Indoors in Basel.

Federer, whose poor form this season has yielded one title and a slump in the rankings to sixth in the world, is battling to reach the eight-man year-end finals in London in early November.

Every win this week and next in Paris will be crucial to him appearing in a tournament he has won six times.

He began with a victory in front of his home crowd on Monday as he beat Frenchman Adrian Mannarino.

Federer has never lost to 48th ranked Istomin in five matches, defeating him most recently at Indian Wells in March despite suffering from a painful back.

Japanese sixth seed Kei Nishikori, losing finalist two years ago to Federer, reached the second round 6-2 6-4 over another 32-year-old Swiss Marco Chiudinelli, a wildcard entry and childhood friend of Federer.

Nishikori next plays Croatian Ivan Dodig, who advanced in just nine minutes as Argentine Carlos Berlocq retired trailing 2-0.

Marcos Baghdatis also reached the second round, winning his first match since late September with a defeat of German qualifier Benjamin Becker 7-6 (10-8) 6-1.

The Cypriot will face the winner from top-seed and title-holder Juan Martin del Potro and Swiss wild card Henri Laaksonen.