Roger Federer fends off rising star Alexander Zverev to march on in London

Roger Federer struck a blow for his generation against the future by beating Alexander Zverev to book his place in the ATP Finals knock-out stages.

The 20-year-old Zverev showed London’s O2 Arena why he will surely become a star of men’s tennis but Federer’s own time is far from finished yet and his class eventually told.

Sixteen years and 19 grand slam titles separate this pair but remarkably it was Federer’s legs that were fresher in the decider, and after two hours and 11 minutes he had won 7-6 (8/6) 5-7 6-1.

It means the 36-year-old is certain to move into this tournament’s semi-finals, even before his final group match against Marin Cilic, while Zverev faces American Jack Sock for the second qualifying spot.

Zverev might rue missed opportunities, having squandered a set point and 4-0 tie-break lead in the first set, but it was concentration and stamina that ultimately proved the difference.

“I’m very excited about his future,” Federer said on court afterwards. “He’s a wonderful guy and is going to be a great player.”

The Swiss remains on course for a record-stretching seventh ATP Finals crown and with Rafael Nadal pulling out injured, now stands as the overwhelming favourite.

Zverev was dictating early on, his electric double-handed backhand more than a match for Federer’s angles and precision, but there were moments too of youthfulness from the German world number three.

An acrobatic forehand flashed long and past a ducking line judge, when a routine finish would have done, while his racket flew spinning into the air on more than one occasion.

Federer cranked up the pressure at 6-5 when a lucky net cord helped create one set point and then a second when his whipped forehand was shown to have just nicked the line.

Zverev saved both before storming into a 4-0 lead in the tie-break, but Federer dug in to claim five points in a row, again with the help of a fortunate net cord.

A Federer forehand wide gave Zverev 6-5 in the tie-break and set point, but he netted. Three more baseline errors from Zverev meant Federer nicked the set.

Federer broke in the first game of the second set but just as he looked to pull away, his focus wavered. Two double faults helped Zverev break back.

It would turn again at the end of the set as Federer mishit a backhand to concede three set points at 6-5 and Zverev this time pounced to force a decider.

Federer rediscovered his groove in the third, however, winning 12 out of 14 points for a 3-1 lead and then sealing the double break after Zverev floated long.

Zverev’s spirit was broken and all that was left was for Federer to complete victory at 5-1, when his opponent’s weary second serve landed out.