Rafael Nadal squeezed through to the quarter-finals of the Monte Carlo Masters after a narrow win over America's John Isner, but Roger Federer's tournament is over after he lost to Gael Monfils.
Federer was playing his first tournament since losing to Novak Djokovic in the Indian Wells final last month and the second seed's rustiness showed as he was beaten 6-4 7-6 (7/5).
The world number two struck an early break in the first set but Monfils twice hit back to go one up before edging a close second-set tie-break to seal victory.
The French number three will now face Grigor Dimitrov, who dumped out defending champion Stanislas Wawrinka with a 6-1 6-2 win.
Nadal was made to work harder for a 7-6 (8/6) 4-6 6-3 victory over Isner and he will now meet fellow Spaniard David Ferrer in the last eight.
The world number five is eager to establish some momentum on clay, his favourite surface, after a disappointing start to the season but was close to losing the first set before Isner squandered two set points.
The American responded strongly in the second set to level but Nadal broke early in the decider before closing out the match.
The nine-time French Open champion remains on course to meet Novak Djokovic in the semi-finals after the Serb eased past world number 52 Andreas Haider-Maurer 6-4 6-0.
Djokovic will first have to overcome Croatia's Marin Cilic, who battled to a 6-3 7-6 (7/5) win over Jo-Wilfried Tsonga, while Ferrer edged through via a 6-2 6-7 (3/7) 6-1 victory over Gilles Simon.
Tomas Berdych and Milos Raonic will meet in the other quarter-final.
Berdych beat Roberto Bautista Agut 7-6 (9/7) 6-4 and Raonic edged past Tommy Robredo 6-3 3-6 6-3.
Source: PA
