Roger Federer's honeymoon at the Monte Carlo Masters ended abruptly when he went down 6-4, 7-5 to fellow-Swiss Stanislas Wawrinka in the third round on Thursday.
World number three Novak Djokovic made sure he did not suffer the same fate as Federer when he overcame a second set hiccup to tame Spain's Albert Montanes 6-1, 6-7, 6-0.
Djokovic and Wawrinka were among the few lucky players to complete their matches as top seed Rafael Nadal and Andy Murray were frustrated by the thunderstorms that wiped out most of the day's play.
Federer and Wawrinka are close friends and captured the Olympic doubles title together in Beijing but on Thursday Wawrinka was in no mood to be charitable towards his more celebrated, and newly married, countryman.
However, once the 13th seed had sealed his first career win over Federer, his celebrations were rather muted.
"It was not an easy match but of course I am happy to have won it," Wawrinka said after completing the match that had been delayed by more than five hours due to rain.
"It is maybe not the most spectacular tennis but it's my most beautiful victory, yes.
"(But) I am a bit embarrassed to celebrate it."
Wawrinka will face Andreas Beck for a place in the last four after the German qualifier beat Argentine Juan Monaco 3-6, 6-2, 7-5.
Federer, who married his longtime girlfriend Mirka Vavrinec on Saturday, decided to take part in the European season's opening claycourt tournament in the last minute.
However, a few minutes after being shown the exit, the second seed refused to blame the defeat on his lack of preparation.
"Well, it's the problem for everyone. Nobody had a preparation. Slim excuse, because it's the same for everyone," he told a press conference.
CLAYCOURT ADJUSTMENTS
Federer acknowledged he needed to make some serious adjustments to his claycourt game.
"I came again this year because it just gives you information going into your practice sessions, what you need to work on," said Federer, runner-up at the principality for the last three years.
"Today definitely my serve wasn't working. I haven't served my best throughout the season, so I have to make sure I get my serve back in ... because I just don't hit the spots when I really want to."
Federer, who has not won a title this year, struggled with his serve and Wawrinka snatched a break on his sixth attempt in the seventh game.
He wrapped up the opening set as the 13-times grand slam winner netted an easy forehand.
Federer dropped serve in the first game of the second set but broke straight back, charging to the net to save another break point at 3-3.
The 27-year-old floundered in the 11th game after sending yet another forehand wide as Wawrinka was serving for the match.
He had two break points but Wawrinka kept his composure to save them and wrapped up the win on his first match point with a backhand winner down the line.
Spain's Fernando Verdasco, seeded seventh, flashed past compatriot and 10th seed David Ferrer with a 6-2, 6-1 victory to set up a meeting with Djokovic.
The Serbian spent more time than he expected on court after throwing away the second set against Montanes.
Djokovic was serving for the match leading 6-1, 5-4 but his game unravelled and Montanes pounced.
The Serb quickly regained his momentum and handed the unfortunate Spaniard a bagel in the final set.
World number four Murray was leading 7-6 1-0 against Italian qualifier Fabio Fognini when the players were forced back to the locker room because of a torrential downpour.
Ecuador's Nicolas Lapentti just had time to win the opening game of his match against Nadal when action was also stopped on centre court.
Argentine David Nalbandian's encounter with Nikolay Davydenko of Russia and Italian Simone Bolelli's match against Croatian Ivan Ljubicic were also called off.