MADRID >> Andy Murray put on another impressive performance on clay Thursday, defeating Gilles Simon 6-4, 6-2 to reach the quarterfinals of the Madid Open.

The second-seeded Murray broke Simon’s serve in the final game of the first set and twice in the second to stay on track to defend his title.

“I didn’t return that well at the beginning,” Murray said. “But when I got into a rhythm, I was able to dictate a lot of points. I used my variety well and served well. He wasn’t able to put me under much pressure on my serve after the first couple of games.”

In the women’s tournament, 19-year-old qualifier Louisa Chirico defeated Daria Gavrilova of Australia 7-6 (1), 6-2 to reach the semifinals.

The 130th-ranked Chirico became the first American teenager to reach the semifinals of a top clay-court event since Ashley Harkleroad in Charleston, South Carolina, in 2003.

Chirico beat 14th-seeded Ana Ivanovic in the second round, and took advantage of the late withdrawal of Victoria Azarenka in the third round. She will next face either 38th-ranked Dominika Cibulkova of Slovakia or wild-card entry Sorana Cirstea of Romania.

Murray’s match against Simon was a rematch of the 2008 final in Madrid, when the British player won his first title at the tournament.

The match at the “Magic Box” was interrupted for a few minutes late in the second set after a spectator fell ill and had to be attended to by paramedics. The match was allowed to resume while doctors stayed on the stands.

Murray’s win in Madrid last year was his first at a Masters tournament on clay. This year, he reached the semifinals of the Monte Carlo Masters, losing to eventual champion Rafael Nadal in three sets.

He will next face either Joao Sousa of Portugal or Tomas Berdych of the Czech Republic.

The 16th-seeded Simon was trying to reach the quarterfinals of a tournament for the third time this season. He had already done so in Miami and Portugal, failing to advance both times.

“It’s obviously very tricky against Simon,” Murray said. “He lulls you into a false sense of security in points. Sometimes the better you hit the ball, the better it comes back. It’s tough to get the balance between being aggressive and being patient.”