MONACO -- Surprised at seeing rival Novak Djokovic go out of the Monte Carlo Masters after an error-strewn performance, defending champion Rafael Nadal acknowledged he enjoyed some luck in reaching the semifinals on Friday.
Quite an admission from the best player in clay-court history, who has won both this tournament and the French Open a record 11 times. But Nadal struggled against fellow left-hander Guido Pella, losing his first three service games to trail 4-1 before recovering to beat the unseeded Argentine 7-6 (1), 6-3.
Top-ranked Djokovic, who has won the tournament twice, earlier lost 6-3, 4-6, 6-2 to 10th-seeded Daniil Medvedev and produced 47 unforced errors.
Djokovic out, Nadal in trouble. It seemed — briefly, at least — that the day might produce two straight upsets.
Especially when Pella served for 5-1.
But he double-faulted, giving the second-ranked Nadal an unexpected reprieve which he took full advantage of.
"That game was decisive, and I was lucky to win that one. After that, the match changed a lot," Nadal said. "Losing the first three games was tough but I found a way at the right time. Sometimes these matches help for rhythm because you suffer."
Before going onto court for his quarterfinal, Nadal spent some time watching Djokovic. Even 17-time Grand Slam winner Nadal, who has lost 28 times in 53 contests against the toughest rival of his career, was surprised.
"Always, when Novak loses, (it) seems strange because he's super solid," Nadal said. "But everybody is human."
Nadal next faces No. 13 Fabio Fognini, who beat No. 9 Borna Coric of Croatia 1-6, 6-3, 6-2.
Fognini has lost 11 of 14 matches against Nadal, but two of the Italian's three wins were on clay. All the wins were in 2015, including a thriller in the third round of the U.S. Open, when Fognini rallied from two sets down.
"He's able to win against everybody when he's playing well," said Nadal, who may need to go up a level.
Nadal imperiously won the title last year without conceding more than four games in a set, but Pella caused him considerable problems and forced 13 break-point chances on Nadal's serve.
Although Nadal leveled the first set at 5-5, he dropped his serve again. It gave Pella the chance to become the first player to take a set against him here since Britain's Kyle Edmund in the second round two years ago.
Pella reached 30-30 but Nadal broke back and forced a tiebreaker — his first here since a third-round win against John Isner in 2015.
A jittery looking Nadal was broken to love serving for the match. Pella could not hold his serve, either.
He saved one match point at 15-40 down but then double-faulted. After 2 hours, 20 minutes on court, a relieved Nadal hugged his opponent at the net.
The last time Nadal failed to reach the last four here was in 2014, when he lost to countryman David Ferrer in the last eight.
Earlier, Medvedev was appearing in the last eight of a Masters tournament for the first time but Djokovic struggled more in the windy conditions.
He double-faulted at 30-30 to give Medvedev his first match point and a backhand winner secured a first win against Djokovic at the fourth attempt.
"He played worse than before and I am gaining more experience," said the 14th-ranked Medvedev, who is chasing a fifth career title.
The 23-year-old Russian next faces unseeded Dusan Lajovic, who also reached a Masters semifinal for the first time when he beat Italian qualifier Lorenzo Sonego 6-4, 7-5.
One Serb can make Sunday's final, but it's Lajovic and not the one people expected.
When Djokovic won the Australian Open this year he secured a third straight Grand Slam title and 15th overall, and in doing so he moved two behind Nadal and five adrift of Roger Federer's record haul of 20.
Since then, his form has wilted.
Djokovic has failed to reach the last four in three straight tournaments, having fallen short at Indian Wells and Miami.
But his focus is bigger and it's further down the line: taking Nadal's crown at Roland Garros.