In a star-studded semifinal, No. 1 Novak Djokovic defeated longtime rival Rafael Nadal in straight sets 6-3 6-3 on Saturday in the semifinals of the Barclays ATP World Tour Finals at London's O2 Arena.

Djokovic came out aggressively from the start, breaking Nadal’s serve early in the first set. Once establishing an early lead, the Serb coasted to a fairly routine 6-3 set win. Djokovic dominated on his own serve, winning 20 of 27 points and finishing the set efficiently in just 34 minutes.

The second set was much more closely battled although Nadal wouldn’t have enough to overcome the three-time defending champion. Djokovic broke Nadal’s serve for a 3-2 lead in the second set as well as the final game of the match to win the set.

It was the 46th time the two champions have met in their storied careers on the court. Djokovic and Nadal hold the record for the most meetings between two players in the Open Era.

The last time the pair met was in the China Open final, with Djokovic notching his sixth Beijing title 6-2 6-2. With Saturday's win, Djokovic drew level at 23-23 in their FedEx ATP head-to-head series. Djokovic is now 8-1 against Nadal since the 2013 U.S. Open.

On Sunday, Djokovic will go for his record fourth straight title in London against the winner of the other semifinal between Stan Wawrinka and Roger Federer.