By Martyn Herman
LONDON (Reuters) - Japan's Kei Nishikori surged to a three-set victory over alternate David Ferrer at the ATP World Tour Finals on Thursday and must now wait anxiously to see if he has done enough to reach the semi-finals.
The 24-year-old lost the opening set to the gritty Spaniard, a late stand-in for injured Milos Raonic, but played beautifully after that to seal a 4-6 6-4 6-1 win -- his second in Group B after also beating Andy Murray.
The result was enough to guarantee six-times champion Roger Federer a place in the semi-finals even before the Swiss walks on court to face home favorite Murray in the evening session.
Should Murray win in straight sets he would top the group, but any other result would send Federer through as group winner with Nishikori runner-up and the Scot packing his bags.
Nishikori found out shortly before walking on court that Ferrer would be on the other side of the net, not the big-serving Raonic, and it took him time to adapt.
"It was really difficult to make this adjustment -- they told me one hour before the match, it was tough to change tactics but I'd prepared well and I'm happy to win today," the Florida-based world number five said.
"The third set was almost perfect."
Near sell-out crowds at the O2 Arena had not been treated to a three-setter at the tournament before Thursday's action but when Ferrer stepped in for a brief cameo role the likelihood was that he would provide a toe-to-toe battle.
Ferrer, beaten in nearly three hours by Nishikori in the quarter-finals of the Paris Masters, a result that scuppered his hopes of qualifying for the year-ender by right, hit back from a break down to snatch a high-quality opening set.
From then on, however, U.S. Open runner-up Nishikori showed why he has become a trailblazer for Asian tennis, unleashing his full repertoire of fiercely struck groundstrokes and silky drop shots to run Ferrer into the ground.
After converting his first set point in the second set with a backhand winner, Nishikori raced ahead in the decider against a tiring opponent who will return home around $85,000 richer for his brief appearance in London.
Earlier doubles second seeds Daniel Nestor (Canada) and Nenad Zimonjic (Serbia) beat Spaniards Marcel Granollers and Marc Lopez in a deciding set tiebreak but it was not enough to keep them afloat in the tournament after two losses.
(Editing by Ed Osmond)