London - Kei Nishikori absolutely has the talent to make the breakthrough and win one of tennis's Grand Slams says his coach Michael Chang.
Chang said the injury-plagued Japanese world number nine needed to hit the majors healthy, make a few adjustments to his game and he could be a match for anyone on the tour.
Though Nishikori made the 2014 US Open final, he has never gone beyond the quarters at the Australian or French Opens, or the last 16 on the grass at Wimbledon.
This year at the All England Club, the 27-year-old slumped to a 6-4, 7-6 (7/3), 3-6, 6-3 loss to Spanish 18th seed Roberto Bautista Agut in the last 32.
"This is a surface he can do well on," Chang insisted.
"When Kei's healthy, I think he can play against the best players in the world on any surface, and especially the way the grass courts are playing now at Wimbledon, it suits a lot of baseliners.
"Hopefully it's just a matter of time. But I don't think his past results here are reflective of what he can do," said the 1989 French Open champion, who also made the 1996 US and Australian Open finals.
"The positive is that he walks away from here healthy. That's going to fare well for him going into the US season. Hopefully he stays healthy for the US Open," the American said.
Nishikori has the sport's dominant big four -- Andy Murray, Rafael Nadal, Roger Federer and Novak Djokovic -- ahead of him, with the likes of Stan Wawrinka, Milos Raonic and Marin Cilic also battling to break into the club.
But Chang, who coached Nishikori to the US Open final, said getting into Grand Slam quarters and semi-finals regularly was not beyond Nishikori's reach.
"To be in that area is not really that far for him; it's trying to get past that into the next stages. But there's a lot of tough opponents along the way.
"He needs to continue to work hard and he needs to stay healthy -- because when he's not then he's very susceptible.
"But he has the talent to do it. He's got to make a few adjustments to his game and to give himself that opportunity. When the opportunity is there, there is a chance for success."
Chang, 45, said managing Nishikori's injuries was a question of finding the balance between those that would be worsened by playing, and nagging problems that can be managed and played through with treatment.
He also had praise for Federer, saying the Swiss great had ushered in a friendlier approach in the locker room than the hostile atmosphere Chang experienced when joining the tour, when the rival camps of John McEnroe, Jimmy Connors and Ivan Lendl would sit in their own corners.
"Roger's not like that," Chang told reporters.
"You can go out and beat the guy's brains out, come back in the locker room and be friends.
"If you look at Roger and Rafael Nadal, if they had bad blood, would it make their rivalry any less special?"