London - Kei Nishikori admits he had mixed feelings when he was drawn to face old friend Christian Harrison in the Wimbledon first round next week.
Nishikori has struggled to play his best tennis at Wimbledon, so the Japanese star would welcome a morale-boosting victory against American qualifier Harrison.
But the 28-year-old knows it could be tricky to stay focused against an opponent he has such a good relationship with.
Nishikori met world number 200 Harrison, 24, while honing his game at the IMG Academy in Bradenton, Florida.
"I know him a lot actually. We practice together all the time in academy. We grow up together. It's not easy when you have to play with good friends," Nishikori told a press conference at Wimbledon on Saturday.
"I hope I can enjoy the match. Actually it's the first time to play in official match, so it's going to be exciting. Hopefully we both play good tennis."
Harrison's extra knowledge of Nishikori's game could pose a problem for the 24th seed as he looks to make a strong start at the All England Club.
Asked if it was an advantage to play someone whose style of play he knows well, Nishikori said: "Sometimes yes, sometimes no. He also knows me a lot, how I play.
"I think it's more advantage than when you have no idea who your opponent is.
"I think I can set up more tactics than normal."
Nishikori arrives in south-west London hoping to get past the Wimbledon fourth round for the first time in 10 attempts.
He admits he has found it tough to shine on grass in the past, with injuries often hampering his bid to replicate his impressive hard-court play.
Nishikori reached the US Open final in 2014 and made the semi-finals in New York two years later, but he has never made it beyond the last eight at any other major.
"Well, for my past, I had couple injuries with this surface," he said.
"I think this surface is the only one I haven't play the best yet.
"I'm trying new things every year. I've got to change my tennis little bit.
"You've got to really use your legs. The point is quick (on grass). It's different than clay, so I've had a couple issues.
"But I enjoy playing grass. You got to use different shots, you got to come in little more than usual.
"I hope I can have a good result this year."