Switzerland's Roger Federer hits a return to Serbia's Janko Tipsarevic during their men's singles tennis match at the ATP World Tour Finals in the O2 Arena in London, Nov 6, 2012. [Photo/Agencies]

LONDON - Roger Federer reached yet another career milestone with victory over Janko Tipsarevic and David Ferrer dipped into his seemingly endless tank of stamina to beat Juan Martin del Potro on the second day of the ATP World Tour Finals on Tuesday.

Swiss maestro Federer glided to a 6-3 6-1 victory over outclassed Serbian Janko Tipsarevic to open his Group B account, taking his haul of victories at the elite year-ending event to 40 having qualified for an 11th consecutive year.

Another silky display from the 17-times Grand Slam champion took him past the record he shared with Ivan Lendl, the level of his play suggesting the 31-year-old world number is still the man to beat at the tournament he has won a record six times.

Ferrer does not glide, rather hustles and bustles his way around the court, driving opponents to distraction with rock-like defences, punchy groundstrokes and speedy footwork.

Del Potro will testify to that after the towering Argentine lost a fascinating duel 6-3 3-6 6-4 in front of a packed audience at the 17,000 O2 Arena alongside the River Thames.

Spain's David Ferrer hits a return to Argentina's Juan Martin Del Potro during their men's singles tennis match at the ATP World Tour Finals in the O2 Arena in London, Nov 6, 2012. [Photo/Agencies]

Fourth seed Ferrer, whose victory was the 73rd of a season that has delivered a career-best seven titles, will face Federer on Thursday trying to gain a first victory at the 14th attempt.

Hardly a cause for optimism in the Spanish camp but on current form few players, not even Federer, will relish a meeting with the player nicknamed the Iron Man.

At least the evening singles was a proper contest.

Federer's demolition of an out-of-sorts Tipsarevic was a non-event, lasting little more than an hour.

The world number two seized the initiative when he broke Tipsarevic's first service game and never looked back.

"I was striking the ball well today," world number two Federer told reporters.

Zero wins

"I hope it's a sign for more to come. I'm happy the first one went so well and it takes the pressure off looking ahead in the next couple of matches."

Serbia's Janko Tipsarevic reacts after losing a point to Switzerland's Roger Federer during their men's singles tennis match at the ATP World Tour Finals in the O2 Arena in London, Nov 6, 2012. [Photo/Agencies]

Tipsarevic, who pulled out of his match at the Paris Masters last week citing illness, qualified for the eight-man tournament as a result of Rafa Nadal's continuing injury woes.

He also went into the match with a zero in the wins column in previous clashes with Federer and there was an air of predictability about the result almost from the word go.