(CNN) -- After a difficult past year, Rafael Nadal is back where he feels most comfortable -- but his rivals are battling to find form ahead of the French Open.
While the Spaniard cruised into the quarterfinals of the Monte Carlo tournament he has won for the past eight seasons, world No. 1 Novak Djokovic again had to come from behind to earn his place while Andy Murray suffered a crushing defeat that will demote him to third in the rankings.
Fourth seed Tomas Berdych and No. 5 Juan Martin del Potro also crashed out Thursday to thin out the competition for Nadal as he continues his winning return to the ATP Tour following longterm knee problems.
His 6-2 6-4 rout of German 16th seed Philipp Kohlschreiber was his 16th successive victory this year following a defeat in the final of his comeback event in Chile in February.
"I feel more relaxed, yes. I had some uneasy moments during the past year," Nadal said after his 44th consecutive win at the clay-court event, which set up a clash with 21-year-old Bulgarian Gregor Dimitrov.
"Now I'm back on the tour. Just being here is good news. And winning matches -- I say it every day, but winning every match is very important to me today. Every time I have the chance to go on court and play well, feel competitive, is a really good feeling."
Dimitrov is also on a roll, having followed up his opening victory over world No. 10 Janko Tipsarevic by beating Germany's Florian Mayer 6-2 6-4.
"Really looking forward to that match," said Dimitrov, who reached a career-high 31st in the rankings last month. "Even for now I'm very excited.
"I'm feeling quite good coming on court with (the top players). I feel also physically I'm ready to kind of hang with them more as the match goes on.
"I know tomorrow is another point of view, since clay court you're playing against the greatest of all time. There's that feeling and anxiety that you want to come out and do the best you can. I think most of all you have to keep a good composure."
Murray is seeking to restore his composure after being beaten in less than an hour by Stanislas Wawrinka, a result that will see the Swiss 13th seed's absent compatriot Roger Federer return to No. 2 in the rankings.
"When I started making a lot of errors he was able to dictate all of the points from there," said Murray, who made 24 unforced mistakes as he missed out on a possible semifinal against Nadal.
"I've played some good tournaments here but it does take me time to feel comfortable on the surface. I need matches against top players to see what's going wrong and going right and the things I need to work on to get better.
"No-one wants to lose matches like that. Hopefully I can use it as motivation to improve because I really need to do a lot of work. I need to work really hard over the next two weeks to get ready for Madrid."
Last year the Spanish capital's experiment with blue clay proved unpopular with most players, and it was banned for this season.
Djokovic was one of the most vocal critics, but this year he is focused on his fitness problems after battling to beat Juan Monaco 4-6 6-2 6-2 on Thursday.
"It's another big test obviously, again a two-hour match," said the Serbian, who injured his ankle on Davis Cup duty earlier this month.
"Obviously I'm not physically feeling my best. Somehow feels that I always miss that half a step. But I'm trying. I'm fighting. After I lost the first set today, I tried to find that inner strength. I found it again. So that's a positive thing. Every day brings a new challenge and we'll see what happens tomorrow."
A two-time runnerup in the principality, Djokovic -- who could again meet Nadal in the final -- will next face Del Potro's conqueror Jarkko Nieminen.
The veteran Finn triumphed 6-4 4-6 7-6 (7-4) against the 2009 U.S. Open champion as he was taken to a tie-break in the decider after the Argentine saved a match-point, before reaching his first Masters-level quarterfinal since 2006.
Berdych lost 6-4 6-2 to 32nd-ranked Italian Fabio Fognini, who earned his first Masters-level quarterfinal appearance -- a clash with French seventh seed Richard Gasquet.
Gasquet, a semifinalist in Miami last month, beat Croatian ninth seed Marin Cilic 7-5 6-4.
Wawrinka, meanwhile, will next face world No. 8 Jo-Wilfried Tsonga, who defeated Austrian Jurgen Melzer 6-3 6-0 the day after the Frenchman's 28th birthday.
"To beat Andy that easy was a big surprise, for sure," Wawrinka said. "I'm playing really good, really strong, really confident with my game. He's playing slow, he's playing from the baseline, he's not putting so much pressure. For me on clay, it's perfect."