Sweden’s Robin Soderling returned to haunt Rafael Nadal at the ATP World Tour Finals on Monday, beating him 6-4 6-4 in their opening Group B round-robin clash. Soderling, who ended Nadal’s 31-match winning streak at the French Open this year, again proved a tough opponent for the Spaniard, whose hopes of knocking Roger Federer off the top of the world rankings are now fading fast. Nadal, who has not claimed a title since the claycourt Rome Masters in May, struggled to handle the powerful Soderling forehand on the faster indoor surface at the O2 arena and looked vulnerable on serve throughout.

Soderling secured the first set by breaking serve in the 10th game and repeated the trick at the same point in the second.

Roger Federer overcame an erratic forehand and Fernando Verdasco on Sunday, rallying to beat his Spanish opponent 4-6 7-5 6-1 in the round-robin stage of the ATP World Tour Finals.

In doubles, third seeds Mahesh Bhupathi and Mark Knowles notched up a 6-4 6-4 win over Frantisek Cermak and Michal Mertinak in their first Group A match on Sunday.