By JEROME PUGMIRE
AP Sports Writer

MONACO (AP) - An erratic Novak Djokovic suffered a surprise 6-3, 4-6, 6-2 defeat against Daniil Medvedev in the Monte Carlo Masters quarterfinals on Friday.

The top-ranked Serb, who has won the tournament twice, looked out of sorts and produced 47 unforced errors.

Defending champion Rafael Nadal was not at his best, either. But the second-ranked Spaniard rallied from 4-1 down against unseeded Guido Pella to win 7-6 (1), 6-3 and move closer to a record-extending 12th title here.

Nadal imperiously won last year without conceding more than four games in a set. So Pella will have regrets, considering he was serving for a 5-1 first-set lead when he double-faulted.

Although Nadal won the next four games to level at 5-5, he dropped his wayward 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.

Although 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.

Nadal next plays No. 9 Borna Coric of Croatia or No.13 Fabio Fognini of Italy. They were playing their quarterfinal later Friday.

Earlier, the 10th-seeded Medvedev was appearing in the last eight of a Masters tournament for the first time but Djokovic struggled more in the windy conditions.

"It's tough to find rhythm and he doesn't give you much rhythm," Djokovic said. "He was very patient and played well tactically."

Djokovic 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, and a first victory against a No. 1.

"He played worse than before and I am gaining more experience," Medvedev said. "He was not so good in the first set and made a lot of mistakes."

The 14th-ranked Medvedev is chasing a fifth career title.

The 23-year-old Monaco resident next faces the unseeded Dusan Lajovic, who also reached a Masters semifinal for the first time when he beat Italian qualifier Lorenzo Sonego 6-4, 7-5.

Lajovic has not dropped a set so far.

"I didn't expect this," the 28-year-old Serb said. "I was sick before the tournament and taking antibiotics."

Djokovic won the Australian Open this year to secure a third straight Grand Slam title and 15th overall, moving two behind Nadal and five adrift of Roger Federer's record haul of 20.

But Djokovic has now failed to reach the last four in three straight tournaments, after also falling short at Indian Wells and Miami.

"I am lacking that determination to go for shots on some points," he said.

At times it looked like Djokovic would take control and he clinched the second set with two aces. But his shot-making was below its usual high standards and his drop shot rarely worked.

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