Novak Djokovic inspired Serbia to victory in the inaugural ATP Cup as his singles win over Rafael Nadal helped his country beat Spain 2-1 in Sydney.

World number two Djokovic, 32, defeated top-ranked Nadal, 33, 6-2 7-6 (7-4) to level the tie after Roberto Bautista Agut beat Dusan Lajovic 7-5 6-1.

Djokovic then partnered Viktor Troicki to a 6-3 6-4 doubles win over Pablo Carreno Busta and Feliciano Lopez.

"I will remember this experience for the rest of my life," Djokovic said.

"It's definitely one of the nicest moments of my career."

Djokovic and Troicki quickly went 3-1 down in the first set of the doubles but the animated Serbian pair won the next five games to take the opening set.

They broke early in the second and maintained their momentum, with Djokovic serving out the match at his first attempt.

Djokovic, the reigning Australian Open champion, did not lose a match during the week-long tournament, claiming six singles and two doubles wins.

"It was a huge team effort," Djokovic said.

"I've been very fortunate and blessed to have an amazing career but playing for your country, with some of my best friends, you can't match that."

The Australian Open begins on 20 January, eight days after the ATP Cup finishes.

Nadal frustrated by crowd

Nadal has now lost his past nine hard court matches against Djokovic, who was barely troubled in the opening set.

The Spaniard was broken in the first game of the match and was visibly frustrated by the pro-Serbian crowd, giving them a sarcastic thumbs-up as he dropped serve again.

Djokovic served out the opening set but was given a tougher test in the second, saving five break points in one 10-minute service game.

Nadal saved two break points with consecutive backhand winners but Djokovic took control of the tie-break, closing out victory as Nadal sent a forehand into the net.

"The respect for both players should be there," Nadal said of the crowd afterwards.

Nadal won the Davis Cup with Spain six weeks ago, which is a similar format to the ATP Cup, and he believes the two events are too close together.

"I think that [scheduling] is a confusion for the spectators, and we need to be clear in our sport," he added.

"And for the health of our sport and for the benefit of our sport, in my opinion, it is mandatory that we fix it."