Roger Federer had problems way before his back began playing up during his defeat to Grigor Dimitrov, according to Martina Navratilova.
World No 3 Federer was dumped out of the US Open quarter-finals after suffering a five-set defeat to Dimitrov last night.
During the fifth set, the Swiss star took a rare medical timeout after damaging his back.
But Navratilova believes there were other problems on show prior to the injury.
“Like never. I thought something was off with him because of his forehand,” Navratilova told Tennis Channel.
“He played so well the last two matches but was inexplicably missing shots which were not uncomfortable.
“When this stuff is happening there is nothing you can do.
“Tennis is such a rotational sport and when you don’t do this you have problems.”
Dimitrov appears to be at the end of a long road back to recovery after slipping well down the world rankings.
The Bulgarian had a number of problems of his own to contend with.
But he now appears to be back to his best and has a great chance to win a maiden Grand Slam title.
“Nothing ruins your game more than serving issues. That just washes away your game,” Navratilova added.
“To fix it is really, really hard.
“It is really nice to see him fixing the serving and mental issues.
“And then he finally beat Roger when he’s never beaten him before.”