David Ferrer has admitted that his victory over Kevin Anderson in round four of the French Open was "tough".
The Spaniard, who is seeded fifth in Paris, saw off the South African in four sets on Monday to reach the quarter-finals.
He will now face defending champion Rafael Nadal in the last eight - a repeat of last year's final at Roland Garros.
"It was tough," Ferrer is quoted as saying by the ATP's official website. "I think in the first and second sets I played very good. I think I did not make too many mistakes. In the third, he played better. He improved his level.
"I played consistent. When I lost the third set, I tried to play more with my forehand, and he was more tired than me at the end of the fourth set."
Ferrer has won two of his last 12 encounters with fellow countryman Nadal.
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