Kei Nishikori says he is convinced he can regain his position in the top ten after battling back from injury.
Nishikori climbed as high as world umber four previously and reached a US Open final, although he has been pegged back by elbow injuries in recent years.
He is back now and has looked much more like his old self as he moved into the Rotterdam quarterfinals, and he believes his frustrations may be finally coming to an end.
"I don't feel certain weakness in specific part of my play, so if I can get top 10 player-like mentality to sink into my mind, I think I can be back into top 10," Kei Nishikori said.
"I'm kind of convinced that I'm getting back my good feelings, at least I don't feel like I'm short of good feelings when [hitting] balls, so I can't use that as an excuse anymore.
"I'm happy to reach the quarterfinal and play decent matches against good players. I'm kind of relieved and motivated by that.
"As long as I have frustration that I can't play as usual, it's difficult to lift me up and that exhausts me mentally too.
"I'm happy that I've got out of that. I had trouble holding my serve in last couple of matches and let my opponents play comfortably, and sometimes I can't get into a match well.
"So I still have things to work on, but I'm almost there."
Nishikori will face Croatian ace Borna Coric on Friday for a spot in the Rotterdam quarterfinals.
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