PARIS, June 1 (Reuters) - Roger Federer's French Open campaign was derailed by reformed playboy Ernests Gulbis on Sunday when the Swiss suffered his worst result at Roland Garros since 2004 in a 6-7(5) 7-6(3) 6-2 4-6 6-3 defeat in the fourth round.
The 2009 champion and fourth seed was second best for most of the match and made an unusually high number of unforced errors - 59 - on the Philippe Chatrier show court to hand the 18th seed from Latvia the biggest win of his career.
"I was a bit all over the place," admitted Federer. "I'm clearly very disappointed and have a lot of regrets now. It was a tough match and Gulbis did a good job to hang around and come back.
"On my side, I wished I could have played a bit better. I feel I should have done better from the baseline and I didn't really get into his service games."
Gulbis chased down every shot, struck his groundstrokes with real venom and fully deserved his first grand slam quarter-final place since 2008, also in Paris.
A man who freely admits he wasted his talent since his breakthrough at Roland Garros six years ago, Gulbis said earlier in the week that he was "jumping on the last-chance train" at 25.
He plays Tomas Berdych of Czech Republic in the last eight after the sixth seed beat American John Isner in straight sets.
"It is the biggest win of my career," said Gulbis. "I've been playing very well in France, winning tournaments in Marseille and Nice and I hope the next one will be here."
Federer last failed to reach the quarter-finals here in 2004 when he was knocked out in the third round.
Gulbis went 4-2 up in the first set when a Federer backhand sailed long as the Swiss peppered the court with unforced errors. Federer, however, broke straight back as a Gulbis forehand went wide and the two players upped the tempo in the tiebreak.
Gulbis went 5-3 ahead when Federer sent a routine smash wide but as the crowd chanted "Roger, Roger" the Swiss pulled back the deficit and a whipped crosscourt forehand won him the set.
His problems of consistency returned, however, in the first game of the second set when he was in command of a service game but allowed Gulbis to come back and eventually seal a break.
Federer broke back immediately, broke again for 5-3 and had two set points in the following game, both of which he wasted. On the first he tried a crowd-pleasing overhead but it was half-hit and Gulbis won the point before taking the game.
At 5-5 it was Gulbis's turn to waste two golden opportunities. On his second break point, the Latvian missed a simple drive down the line to win the point. He smashed his racquet on the court and stamped on it, breaking the frame.
He received a warning from the umpire and his 32-year-old opponent won the game with an ace.
In the tiebreak, Federer was leading 3-2 but a series of unforced errors led Gulbis to win five points in a row and take the second set.
Two poor shots by Federer, a backhand hooked wide and then a weak backhand into the next, gave Gulbis a 4-2 lead in the third set and he broke again to take the set on his first set point when Federer hit a forehand long.
The main question seemed to be whether the Latvian's volatile temperament would bubble to the surface as the finishing line loomed.
Federer's game was so off-key, he was going to need help to stay in the tournament and he received it in the fourth set when some Gulbis errors earned him a 5-2 lead.
The 25-year-old Gulbis was granted a medical treatment break and when he returned he appeared rejuvenated, breaking Federer's service immediately for 5-3, on the way to winning 10 of the next 11 points.
He had chances in the following Swiss service game too but Federer, living close to the edge, hung on to win the set on his first set point.
Gulbis broke early in the fifth set as Federer's form suffered another slump and it went with service until Gulbis served for the match.