Kei Nishikori has insisted he is fit to launch his Wimbledon challenge after the world No.5 suffered a calf injury scare.

Japanese star Nishikori is set to face Italy's Simone Bolelli in the first round at the All England Club, but the 25-year-old's involvement in the tournament was in doubt last week when he was forced to retire from his semi-final clash with Andreas Seppi at Halle.

MURRAY TO REGAIN WIMBLEDON CROWN? Andy Murray heads to Wimbledon looking to reclaim the Wimbledon title he won in 2013, once again on the back of triumphing at Queen's Club. Unibet have the Briton as second favourite behind reigning champion Novak Djokovic. UNIBET WIMBLEDON ODDS

Andy Murray 12/5

Novak Djokovic 27/20

Roger Federer 13/2

Rafael Nadal 17/1

Stan Wawrinka 17/1

Kei Nishikori 33/1

Grigor Dimitrov 33/1

Tomas Berdych 40/1

Marin Cilic 40/1

Milos Raonic 40/1

Nishikori sustained the problem in his left calf against Jerzy Janowicz in the last eight and appeared to aggravate it further when he faced Seppi.

But speaking to reporters on Saturday in the build-up to Wimbledon, which gets underway on Monday, Nishikori insisted he would be fighting fit for his first-round match.

"It's good, I should be fine for Monday," he said. "I had a good three matches in Halle. I think it's great preparation for here. I'm sure that I'll have a lot of confidence. I'm feeling good on grass."

Nishikori is seeded fifth for the grass-court grand slam, making him the highest-seeded Japanese player at Wimbledon in the Open era. But the former U.S Open runner-up has never been beyond the fourth round at SW19 - a record he is determined to improve upon this year.

"I think I'm getting close," he said. "I'm not winning a lot of titles yet, but I beat Novak [Djokovic] and Roger [Federer] a couple of times. The next goal is to win a Masters or a grand slam. I hope I can have a good season and get closer to the top guys.

Nishikori will face world No.56 Bolelli, a player he narrowly beat in five sets at Wimbledon last year in their only previous meeting.

"I'm playing Simone, it's going to be tough for sure," Nishikori said. "We played five sets last year. He's good on grass. "But I'm feeling good. I will focus on the first match and play a good match. "The first round, it's never easy. I'm going to have to fight through."