Rafa Nadal was forced to work hard for his 18th straight match win at the Monte Carlo Country Club as he fought back to beat Argentina Guido Pella 7-6(1) 6-3.
The 11-times champion made a sluggish start and was one point away from 1-5 deficit in the opening set but recovered well to convert seven of his 13 break-point opportunities and advance after two hours and 20 minutes.
"It was a very tough first set physically and mentally, too. Losing the first three games with my serve was tough but I found a way at the right time," Nadal said after his win. "I was lucky at 4-1, he had two points to be 5-1 and with 5-1 it's almost impossible. I was lucky to escape that moment and then I played better. ...
"I'm very happy to be through. Being in the semifinals again here means a lot to me."
Nadal has now won 25 consecutive sets on Court Rainier III since dropping one in his opening match in 2017 to Briton Kyle Edmund.
The Spaniard will face 13th-seeded Italian Fabio Fognini, who notched a 1-6, 6-3, 6-2 victory over ninth-seeded Borna Coric of Croatia in the quarterfinals.
Fognini converted his third match point to end the match in one hour, 59 minutes.
