Houston - Spain's Feliciano Lopez got his ATP title defense in Houston off to a smooth start on Wednesday with a 6-3, 6-3 win over American Sam Groth.
Lopez, ranked a career-high 12th in the world and the top seed in the clay court tournament, booked a quarter-final clash with eighth-seeded American Sam Querrey.
"I'm very pleased to be here again," the 33-year-old Spaniard said.
"I need a few more matches to start moving better and hitting the ball cleaner, but it was very difficult because he was serving huge.
"I think I did quite good overall."
Querrey advanced with a 6-1, 4-6, 6-4 victory over compatriot and friend Steve Johnson.
"It's not fun," said Querrey of playing a pal. "I'm definitely glad I won, but it doesn't quite feel the same."
Third-seeded South African Kevin Anderson, who like Lopez had a first-round bye, defeated Argentina's Federico Delbonis 6-7 (4/7), 6-0, 6-3.
"I felt I was moving quite well," Anderson said. "There were a few sort of hesitancies as far as where I was on clay, and I think I far exceeded that. He was a very tough opponent, so I had my work cut out for me today."
Anderson next faces seventh-seeded Jeremy Chardy of France, a 6-3, 6-3 winner over Japan's Go Soeda.
"He's a very talented guy," Anderson said of Chardy. "We've played doubles a few times, so he's one of my good friends on the tour. I'm going to have to play well."Results from the ATP Men's Clay Court Championships in Houston on Wednesday (x denotes seeding):
Feliciano Lopez (ESP x1) bt Samuel Groth (AUS) 6-3, 6-3
Sam Querrey (USA x8) bt Steve Johnson (USA) 6-1, 4-6, 6-0
Jeremy Chardy (FRA x7) bt Go Soeda (JPN) 6-3, 6-3
Kevin Anderson (RSA x3) bt Federico Delbonis (ARG) 6-7 (4/7), 6-0, 6-3