Djokovic joins Federer in World semis

Novak Djokovic booked his place in the semi-finals of the ATP World Tour Finals at the O2 Arena. Picture: Adam Davy/PA Wire

The world No 1 needed just one set to be sure of his berth in the last four and duly delivered, taking the set 6-3.

Djokovic will now meet Rafael Nadal in the semi-final at the O2 Arena on Saturday.

Earlier, Roger Federer made it three wins out of three with a 7-5, 4-6, 6-4 victory over Kei Nishikori.

Federer was already guaranteed a place in the semi-finals courtesy of his straight-sets wins over Tomas Berdych and Djokovic but battled for two hours and 10 minutes to maintain his unbeaten record.

Nishikori fought back from 4-1 down in the second and third sets but ultimately it was to no avail and his hopes of reaching the last four are now over.

Federer has drawn attention not just for his tennis this week - this is the 13th time in 14 appearances he has reached the last four - but also his growing beard.

Whether it is here to stay is still up for discussion in the Federer household.

He said: “If it itches too much, I’ll take it off. If my girls can’t stand it, I’ll take it off. If I look in the mirror and I don’t like it, I’ll take it off. Maybe I’ll think of Santa and keep it. It’s around the corner. I don’t know yet.”

The match was an antidote to all the one-sided clashes the O2 Arena has witnessed.

Federer and Nishikori are two of the most watchable players around and both produced some exquisite play.

Nishikori burst into life midway through the opening set to turn a 3-1 deficit into a 4-3 lead but Federer dug his heels in to level again and took the first set when his opponent netted a backhand.

The match looked over at 4-1 to Federer in the second set but, helped by surely one of the worst shots the great man has ever played - a forehand shank from on top of the net - Nishikori won five games in a row.

History looked to be repeating itself in the decider but this time Federer stopped the rot and buried a smash on his first match point to make it 51 wins in 14 appearances at the tournament.