Novak Djokovic said his first-round win over Kei Nishikori at the Madrid Open was “exactly” what he needed for his confidence after a run of poor form.

The 30-year-old former world number one has failed to reach the quarter-finals in five tournaments since returning from elbow surgery in January.

But he impressed in beating Nishikori 7-5 6-4 to set up a potential second-round tie with Britain’s Kyle Edmund.

“It was exactly what I needed for my confidence,” said the Serbian.

The 12-time Grand Slam champion, now ranked 12th in the world, said earlier this month that his confidence had been knocked by making a premature return two months after surgery.

British number one Edmund faces Russia’s Daniil Medvedev on Tuesday.

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“I was looking forward to these kind of matches, looking to try to win these kind of matches,” said Djokovic, who split with former head coach Andre Agassi in April.

“I couldn’t ask for a better start. I feel much better about everything that is happening on the court and around tennis in general than maybe two months ago.”

The victory was Djokovic’s first against a top-20 opponent since beating Gael Monfils at Eastbourne in June last year, with the Serbian having to abandon his Wimbledon quarter-final against Tomas Berdych in July because of the elbow injury.

World number 20 Nishikori, who lost to Rafael Nadal in the final of last month’s Monte Carlo Masters, is also making his way back up the rankings after missing six months with a wrist injury.

Elsewhere on Monday, Canada’s world number 24 Milos Raonic beat Argentine qualifier Nicolas Kicker 6-3 6-2 to set up a second-round match against third seed Grigor Dimitrov.

Argentina’s Diego Schwartzman defeated France’s Adrian Mannarino 6-1 6-3 and will next play Spain’s Feliciano Lopez, who beat compatriot Pablo Andujar 7-6 (7-4) 6-3.

Benoit Paire hit 39 winners to upset fellow Frenchman and 15th seed Lucas Pouille 6-2 6-3 to set up a tie with Canada’s Denis Shapovalov.