
Novak Djokovic remains on course for a fourth straight title at the World Tour Finals after beating Rafael Nadal 6-3 6-3 in London.

Nadal, despite his recent upturn, can't figure out a way to defeat Djokovic. He's lost eight of their last nine meetings.

Indeed he must be wondering what he has to do to finally beat Djokovic.

Djokovic meets Roger Federer, left, in a repeat of the 2014 final -- though the Swiss pulled out with a bad back last year. Federer on Saturday breezed against fellow Swiss Stan Wawrinka 7-5 6-3.

Rafael Nadal celebrates after he beat David Ferrer 6-7 (2-7) 6-3 6-4 at the World Tour Finals Friday. He ended the group stage 3-0.

Ferrer slumped to 0-3. But he had his chances. Leading 4-3 in the third, he couldn't convert when up 30-0 on the Nadal serve in the eighth game.

Nadal improved to 24-6 against Ferrer and took a 5-4 lead on hard courts.

Up next for Nadal in the semifinals is world No. 1 Novak Djokovic. Djokovic, the defending champion, has won seven of their eight previous matches.

Stan Wawrinka, right, clinched second in the group after beating Andy Murray 7-6 (7-4) 6-4. Wawrinka now faces Roger Federer in a repeat of last year's semi won by Federer in three dramatic sets.

Roger Federer had already qualified for the semifinals at the World Tour Finals before he faced Kei Nishikori Thursday. But he still prevailed 7-5 4-6 6-4 in a pulsating contest.

Nishikori trailed by a break in each set, including being down 4-1 in the third. But he kept things close.

He was let down by a double fault in the last game on game point. Nishikori was eliminated after making the semis last year.

Novak Djokovic finished second behind Federer in Group Stan Smith after beating Tomas Berdych 6-3 7-5. Djokovic faces Rafael Nadal in the last four.

Wednesday's standout match at the World Tour Finals pitted Rafael Nadal, right, against home favorite Andy Murray. Nadal continued his recent revival by beating the Scot 6-4 6-1.

Murray was temporarily deprived of locking up the year-end No. 2 ranking. After a competitive first set that lasted about an hour, he wilted in the second.

A large crowd at the O2 Arena took in the affair. Nadal will be playing in front of the fans again on Friday against pal David Ferrer knowing he has already made the semifinals.

He officially progressed after Stan Wawrinka, right, beat David Ferrer 7-5 6-2 later Wednesday. The winner of Wawrinka-Murray on Friday will join Nadal in the last four.

Novak Djokovic, left, and Roger Federer renewed their rivalry at the World Tour Finals on Tuesday.

For a change from current form, it wasn't the world No. 1's day. He lost 7-5 6-2 to see his 23-match winning streak come to an end.

Federer improved to 2-0 in Group Stan Smith and qualified for the semifinals. He is the record six-time champion at the year-end championships.

Kei Nishikori got his first win at this year's event, beating Tomas Berdych 7-5 3-6 6-3 in the tournament's first three-set match of 2015.

Berdych missed out on his first win. He fell to 0-2 in group play and is close to elimination.

Andy Murray made his entrance at the World Tour Finals on Monday and took on David Ferrer.

Murray beat Ferrer in Paris less than two weeks ago and did it again at the year-end championships, prevailing 6-4 6-4.

Ferrer, who was the runner-up in 2007, has now lost seven of his last eight matches against the Scot.

Ferrer's fellow Spaniard, Rafael Nadal, had better luck later Monday. He routed a misfiring Stan Wawrinka 6-3 6-2.

Nadal served well against Wawrinka, and other parts of the 14-time grand slam winner's game were working well, too.

But Wawrinka had a night to forget. He committed 35 unforced errors a little over a week after defeating Nadal in Paris.

Novak Djokovic, the dominant world No. 1, began the tournament by thrashing Kei Nishikori on Sunday.

The elite eight in London, from left to right: Kei Nishikori, David Ferrer, Stan Wawrinka, Andy Murray, Novak Djokovic, Roger Federer, Rafael Nadal and Tomas Berdych.