Monaco, April 20 -- 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 l...