Sleepless nights for Japan tennis coach

Kei Nishikori, Go Soeda and Tatsuma Ito are sharing accommodation with the long-suffering Murakami at the athletes' village in Olympic Park, unlike some of the top tennis stars who have opted to stay nearer Wimbledon.

"These three are really best buddies so sometimes I'm worried about that but all three respect each other and help each other and some of them have known each other since their junior years," said Murakami.

"Because they're in the next room they're loud. From sundown they're just loud."

Here they're trying to be respectful but when they get back to their room they're loud. They switch to a different personality," he joked at a press conference.

"Tatsuma is in my room so I feel bad for him but he wakes up very early and he wakes me up which I don't like about him."

The star of the Japanese tennis team is Nishikori, who has shot up the rankings with some impressive performances.

Nishikori is gunning for Japan's first Olympic tennis medal since 1920.

Ichiya Kumagai won a silver in the men's singles at the 1920 Antwerp Games and also took silver in the men's doubles in the same year with Seiichiro Kashio. They are Japan's only two Olympic tennis medals.

"It's a completely different situation from four years ago," said Nishikori, the 22-year-old 15th seed who crashed out in the first round in 2008.

"I was 17/18 and now I have more confidence and have a better ranking. Everything's different from the Beijing Olympics."

"It's going to be on grass so it's going to be tough for me but hopefully I can get good results and get a medal.

That's my goal," added Nishikori, who has a tough-looking opener against Australian teenager Bernard Tomic.

Nishikori said he was comfortable in London but that Wimbledon would feel different from usual, with players wearing coloured clothes rather than the traditional white demanded at the Grand Slam that finished last month.

His room-mate Soeda, ranked 47, will meet Marcos Baghdatis of Cyprus while 69th-ranked Ito, 24, goes up against Canadian giant Milos Raonic.

Nishikori and Soeda, 27, face a daunting task in the doubles against Swiss defending Olympic champions Roger Federer and Stanislas Wawrinka.

"I think we'll be naturally nervous but I don't want to think about it too much just because it's Federer. We just want to think about what we need to accomplish at the Games and keep focused," said Soeda.