Top-seeded Andy Murray threw away a 4-0 lead in the deciding set of his third-round match on Thursday as 15th-seeded Albert Ramos-Vinolas won 2-6, 6-2, 7-5 at the Monte Carlo Masters.
Murray, who is returning after a spell out with a right elbow injury, looked rusty and struggled on his serve in a match lasting more than 2 ½ hours.
Ramos-Vinolas faces fifth-seeded Marin Cilic in the quarterfinals. The Croatian reached the last eight after beating No. 9 Tomas Berdych 6-2, 7-6 (0).
In their first-ever meeting, a double break put top-ranked Murray 4-0 up in the decider but 24th-ranked Ramos-Vinolas broke back twice to level the match at 4-4.
Murray struggled in the ninth game, taken to deuce before finally holding and then unsuccessfully pressuring the Spaniard's serve in the next game. After breaking Murray's serve again, Ramos-Vinolas served out the match on his second serve.
In a match between powerful hitters, Cilic was serving for victory at 5-4. After a long game Berdych broke back for 5-5 and then forced a tiebreaker, but the Czech player wilted against the 2014 U.S. Open champion.
No. 2 Novak Djokovic, No. 3 Stan Wawrinka and defending champion Rafael Nadal were all in action later Thursday.
Wawrinka plays No. 16 Pablo Cuevas; No. 4 Nadal takes on No. 14 Alexander Zverev, and Djokovic plays No. 13 Pablo Carreno Busta.