(Fixes typo in intro)
By Robert Woodward
PARIS, June 1 (Reuters) - Ernests Gulbis has learned a lesson from Novak Djokovic and is determined to focus his energy on his tennis career.
The fruits of the Latvian's change of direction, after years of bad choices and misspent evenings, were seen at the French Open on Sunday when he sealed the biggest win of his career with a five-set defeat of Roger Federer in the fourth round.
Not that the victory over the former champion was devoid of the old Gulbis style after he smashed a racket, stamped on it and then gave it to a young boy in the crowd as a memento.
"I have to break at least one racket on every court in the world otherwise I would show too much disrespect to the Paris centre court and I cannot allow this," he told reporters of the gesture which earned the 25-year-old a warning from the umpire.
The crowd were loud in their support of Federer and Gulbis was happy in his role of villain of the piece.
"For my confidence and just for me as a tennis player, a five-set win over Roger Federer is really big.
"Hopefully, it's going to change me, that I become more comfortable about myself on a tennis court. Change is good, everybody changes, changes comes, you know.
"With Novak, it's just a normal thing from being a young kid growing up in Munich Academy. We used to go out together, in a nightclub, and then after all the success, he has to be more focused.
"You cannot spend life energy on so much stuff, because everybody wants a piece of you then. So you have to block yourself in a way and you mustn't lose your inner beliefs.
"I can just try to make an impression, but also sometimes you don't want to make an impression."
Gulbis was well worth his victory after he returned revived from a medical treatment break, at 5-2 to Federer in the fourth set. He broke Federer's service immediately on his return, on the way to winning 10 of the next 11 points.
"If I'm honest, I'm not big on medical timeouts," Gulbis said. "I don't like it but I take it when it's really necessary. It probably was my third medical timeout in my life.
"I was scared a little bit to pull a muscle and I had already a tear in the muscle in that area. I was just being cautious."
Federer said he had no problems with medical timeouts but seemed to cast doubt on Gulbis's motives.
"He didn't look hurt in any way, but if you can use it, might as well do it," he said.
"Clearly you don't want anybody to abuse it. I hope that Ernests didn't.
"As long as integrity is fine and the players do it for obvious reason, it's okay. If it's just to disrupt play for the other guy, then clearly it's not really nice, not very fair."
Editing by Ed Osmond