Rafael Nadal had dropped only nine games in his previous five sets against Guido Pella, but the Spaniard was forced to work hard for his 18th straight match win at the Rolex Monte-Carlo Masters on Friday, defeating the Argentine 7-6(1), 6-3. “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. “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 semi-finals again here means a lot to me.”The 11-time champion, who found himself one point away from a 1-5 deficit on three occasions in the first set, is now within two wins of his 12th title at the Monte-Carlo Country Club. Nadal converted seven of 13 break points to advance after two hours and 20 minutes. Nadal has now swept 25 consecutive sets on Court Rainier III since dropping the second set of his opening match in 2017 to Kyle Edmund. Pella became the first man since the Brit to earn more than four games in a single set against the 11-time champion at this event.Nadal is now just one win away from his 13th championship match (11-1) in the Principality, following wins against Australian Open quarter-finalist Roberto Bautista Agut, 2017 Nitto ATP Finals champion Grigor Dimitrov and Pella. The 32-year-old will meet Borna Coric or Fabio Fognini in the semi-finals. The Spaniard improves to 71-4 at the third ATP Masters 1000 event of the season. The last player to defeat Nadal at this tournament was Novak Djokovic in the 2015 semi-finals. Djokovic is responsible for two of Nadal’s four losses (2013, ’15). The only other men to defeat Nadal in the Principality are David Ferrer (2014) and Guillermo Coria (2003).Pella did not show any nerves when faced with the prospect of playing 11-time champion Nadal on Court Rainier III. The Argentine raced into a 4-1 lead, attacking the second seed’s forehand and moving up the court in crucial moments to break the Spaniard in his opening three service games. But Nadal found his way back into the set and, after trading breaks at 5-5 to reach a tie-break, the 80-time tour-level titlist charged into a one-set lead. Nadal dropped only one point in a dominant tie-break, playing with consistent depth to force Pella into defensive positions. This year’s Australian Open finalist fired a backhand passing shot up the line to earn six set points, taking advantage of his second opportunity with an overhead.Once again, Nadal found the target with a backhand up the line en route to a break in the opening game of the second set. The 32-year-old soon doubled his advantage to lead 4-1 with an angled cross-court forehand and, despite failing to serve out the match, Nadal broke Pella for the seventh time to reach the last four.“He’s playing a great season and winning a lot of matches on clay, playing one final, winning in Sao Paulo, playing the semi-finals in Buenos Aires,” Nadal said of Pella. “[It’s a] lot of matches in a row for him and he has plenty of confidence.” Pella was aiming to reach his first Masters 1000 semi-final after an impressive start to the 2019 season. The Argentine, who owns a 17-8 record this year, advanced to two ATP Tour championship matches during the ‘Golden Swing’ in February. After falling to Juan Ignacio Londero in the inaugural Cordoba Open final, Pella defeated Cristian Garin to lift his first ATP Tour title at the Brasil Open.