By Martyn Herman
LONDON (Reuters) - There is no let-up for Roger Federer as he prepares for his 12th consecutive appearance at the ATP's season-ending extravaganza.
The oldest player in the eight-man ATP World Tour Finals draw at 32 and a six-times former champion will begin on Tuesday against world number two Novak Djokovic, having come tantalizingly close to beating the Serb in the Paris Masters semi-finals at the weekend.
Wins over the big guns are becoming something of a rarity for the 17-times grand slam champion whose days of lording it over the sport may be over but whose box-office appeal never fades.
For the first time in more than a decade Federer's place in the Finals was in jeopardy after a season, which by his own sky high standards has been lean, left him facing an undignified scrap for points as the European summer turned to Autumn.
Thankfully for the ATP, especially with British favorite Andy Murray absent after back surgery, Federer's strong run in Basel where he lost to Juan Martin del Potro in the final and at the Paris Masters guaranteed his place.
The world number six may not be a title favorite when play begins alongside the River Thames at the O2 Arena, but few would wager much money against him producing a timely reminder of his powers as he aims to hold back the sands of time.
But an opener against Djokovic is a tough proposition.
"It's unusual, no doubt about it, back to back matches against Novak," Federer, who was a set and a break up against the Serb on Saturday before being overpowered, said.
"But I'm always excited about these challenges."
Federer, who has won only one title this year, faces a daunting task just to reach the semi-finals with Del Potro and Frenchman Richard Gasquet also in his section.
Del Potro was robbed of his possessions at Paris's Gare du Nord on his way to London and will no doubt be keen to unleash his anger on Gasquet who has qualified for the tournament for the first time since 2007 despite being only ranked nine - a beneficiary of Murray's ill-fortune.
"It's the first time something like this has happened to me. I'll try to enjoy the tournament and not let this affect me," Del Potro said.
"I arrived to this tournament with the remaining energy I have."
Play begins in the huge auditorium, usually reserved for the world's biggest music acts, on Monday in Group A with Czech Tomas Berdych, in his fourth consecutive appearance in London, taking on Swiss debutant Stanislas Wawrinka.
World number one Rafa Nadal, who could theoretically lose his top ranking to Djokovic if he flops badly at a tournament he is yet to win in a glaring omission from his CV, will begin on Tuesday against compatriot David Ferrer with the sour taste of his semi-final defeat in Paris still in his mouth.
"When he's playing well, he's very dangerous on all the surfaces, but especially on this one, because it's probably the worst surface for me," Nadal, who has won an incredible 10 titles since returning from a lengthy injury layoff in February, said after his Paris defeat.
(Editing by Ed Osmond)