Galloped away

One break was enough for Federer in the opening set and after he pounced again to break for a 2-1 lead in the second he galloped away to victory, the 876th of his career to move into third place of all time ahead of John McEnroe.

A multiple exposure photograph shows Argentina's Juan Martin Del Potro as he serves to Spain's David Ferrer during their men's singles tennis match at the ATP World Tour Finals in the O2 Arena in London, Nov 6, 2012.[Photo/Agencies]

Ferrer fought off a break point against the towering Del Potro, runner-up here in 2009, before moving 3-1 ahead when the former US Open champion missed a backhand volley.

That proved enough for the Spaniard to take the opening set and he was still the dominant force at the start of the second set when he carved out four break points at 1-1, only for Del Potro to dig himself out of a gruelling service game.

The escape seemed to galvanise Del Potro who began clattering some heavy groundstrokes to gain a decisive break in the second set and set up a decider.

Ferrer stormed into a 4-1 lead only for Del Potro to drag himself right back into contention at 4-4.

Ferrer, who arrived on a 10-match winning streak after indoor titles in Valencia and Paris, refused to panic, however, and he rattled off the last eight points of the match to seal victory in two hours 16 minutes.

"I am very, very, very happy. It was a top match, and it was very difficult to play against Juan Martin," Ferrer said.

"I don't know the secret of my good form. It has been the best season of my career."

The focus returns to Group A on Wednesday when US Open champion Andy Murray and world number one Novak Djokovic, who both won their opening matches, meet in a highly anticipated showdown.