Nishikori, Dimitrov claim first round wins in Rome

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Fifteenth seed Dimitrov was too powerful for Italian wildcard Mager, beating him 7-5 6-1 in 74 minutes, and will face Yoshihito Nishioka or Generali Open winner Miomir Kecmanovic in the next round. 

Nishikori, who has suffered with injury over the past 12 months, overcame Albert Ramos-Vinolas 6-4 7-6 (7-3) and could face three-time Grand Slam champion Stan Wawrinka if he defeats Lorenzo Musetti on Tuesday.

"I'm very happy to win," Nishikori said. "I think winning is most important for now. I need to get a lot of confidence. It's been a long time since the US Open last year. It isn't perfect yet, but hopefully one by one I'll get better.

"I tried to be aggressive when I could. He hits a lot of topspin balls, so it's not easy, but I tried to have good defence and good offence."

Hubert Hurkacz dumped out Great Britain's Dan Evans in three sets, while Marin Cilic overcame Alexander Bublik 6-7(7-4), 6-2, 6-4 to set up a meeting with sixth seed David Goffin. 

Seeds Felix Auger-Aliassime and Karen Khachanov, meanwhile, slipped to defeats to Filip Krajinovic and Casper Ruud respectively. 

The second round will see top seeds Novak Djokovic and Rafael Nadal in action after they were handed first-round byes.