World number one Novak Djokovic booked his place in the second round of the US Open with victory over Spaniard Roberto Carballes Baena.

The Serb three-time champion won 6-4 6-1 6-4 to kick-off the defence of his title at Flushing Meadows.

Djokovic has reached the final on his past three appearances in New York but was taken to four sets in his opening two rounds last year.

He faces American Sam Querrey or Argentine Juan Ignacio Londero next.

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Meanwhile, Russian fifth seed Daniil Medvedev took just 85 minutes to see off Indian world number 88 Prajnesh Gunneswaran with a routine 6-4 6-1 6-2 win.

The 23-year-old, who has reached three consecutive tour finals this year, will face Bolivian world number 84 Hugo Dellien in round two.

“I can’t say I’m feeling amazing about my game but to win by that score in the first round is great,” he said. “I hope I can continue to play well.”

Medvedev, who won the Cincinnati title earlier this month, is widely tipped as the man to put an end to Djokovic, Roger Federer and Rafael Nadal’s dominance.

“I always try to stay at the same time a little bit away [from such talk], because I always say at this moment of my career I haven’t even been in the quarters of a Slam yet,” he said.

“So that’s the first step to make, and if I make this step, then I can talk about bigger goals and bigger achievements.”

Elsewhere, Japanese seventh seed Kei Nishikori raced into the second round when he took a 6-1 4-1 lead before Argentine opponent Marco Trungelliti, 29, retired with a back problem.

“It’s a little bit sad to see. He’s a great player,” said Nishikori, who faces 108th-ranked American Bradley Klahn in the next round.

“I played great tennis from the beginning and I’m happy with the way I played. But honestly, I wanted to play a little more because I was feeling good on the court and I wanted to get a little more confidence.”

But Italian 11th seed Fabio Fognini lost 6-3 6-4 6-7 (6-8) 6-3 to American 21-year-old Reilly Opelka, who will face Spaniard Jaume Munar or German qualifier Dominik Koepfer in the next round.