Roger Federer has been getting used to early exits at grand slams but rated his French Open loss to Ernests Gulbis as the most disappointing of the lot.
Having made 36 consecutive slam quarter-finals, Federer has failed to reach the last eight at three of the last four tournaments.
The sequence ended at Wimbledon last summer with his stunning second-round loss to Sergiy Stakhovsky while he was then beaten in the fourth round at the US Open by Tommy Robredo.
In Paris, Federer came out on the wrong end of a five-set battle with Gulbis in round four, losing 6-7 (5-7) 7-6 (7-3) 6-2 4-6 6-3.
"For every match you can't necessarily explain why you lost," said Federer. "Sometimes you're more disappointed, sometimes less. I'm not mad, but I'm not happy, either. Because I missed too many opportunities. I did not play like I wanted to play.
"This time I was in good shape, and I think I could have done better. That's why I'm probably even more disappointed this time."
Gulbis appears to have left his playboy reputation behind him, if not his penchant for causing controversy, and is finally living up to his considerable talent.
From outside the top 130 in the rankings at the start of last season, Gulbis has climbed to a career-high 17 and is unbeaten in France this year having won titles in Marseille and last week in Nice.
He said: "It's probably the most important win, especially because it was five sets.
"I beat him before, but it was a three-set match. So for my confidence and just for me as a tennis player, a five-set win over Roger Federer, it's really big."
Andy Murray had an uncomfortable night but showed once again he is a master of tennis' tightest moments as he battled past Philipp Kohlschreiber and into the fourth round.
The pair had been locked at 7-7 in the deciding set when darkness descended on Saturday, giving the Wimbledon champion no margin for error when the match resumed around 16 hours later.
"I didn't sleep much," said Murray. "I kept waking up. I was ready to play at four or five in the morning. It's not easy coming back at 7-7 in the fifth set."
Murray practiced right up until walking out to resume play and after 40 minutes of tense, competitive tennis he emerged a 3-6 6-3 6-3 4-6 12-10 winner.
Novak Djokovic made short work of clearing a potentially major hurdle as he crushed Jo-Wilfried Tsonga to move into the quarter-finals of the French Open.
Djokovic wants to win the Roland Garros title more than any other, and few would bet against him if he can maintain the form he showed in a 6-1 6-4 6-1 victory.
Maria Sharapova engineered quite a turnaround to reach the French Open quarter-finals, taking the last nine games and beating Samantha Stosur 3-6, 6-4, 6-0.
After dropping the first set, Sharapova trailed 4-3 in the second. But she didn't allow Stosur another game, reeling off 22 of 25 points.
Eugenie Bouchard reached her second successive grand slam quarter-final by beating eighth seed Angelique Kerber.
The 20-year-old made her grand slam breakthrough in January with a run to the semi-finals at the Australian Open and her progress in Paris has been just as impressive.