HOUSTON -- Lithuania's Ricardas Berankis beat second-seeded Tommy Haas of Germany 6-3, 6-3 on Thursday night in the second round of the U.S. Men's Clay Court Championships.
Berankis, ranked 77th in the world, will face fifth-seeded John Isner, a 7-5, 6-7 (3), 7-6 (3) winner over fellow American Jack Sock.
"This time I had the advantage because it was my second match on clay and his first," Berankis said. "That was an advantage for me and I used it well today. ... I'm happy with today I was lucky in a couple of points but sometimes that happens.".
Top-seeded Nicolas Almagro of Spain overcame a slow start to beat Gael Monfils of France 2-6, 6-0, 6-3.
"I didn't think I played too well in the start," Almagro said. "I was nervous. He's a pretty good player and he was one of the top players a few years ago and he's coming back. I wasn't comfortable being down 6-2 in the first set. I tried to clear my head and that kept me in the match."
Fourth-seeded Sam Querrey, the top American in the world at No. 20, withdrew before his match against Rhyne Williams because of a strained right pectoral muscle.
"When I was warming up today I went hard to test it and if I had one more day or maybe two, I think it would be good," Querrey said. "It's just extreme fatigue in my pec and when I go up to serve and on forehands it catches it and it's achy and painful and I just don't want to tear it."
Querrey won't play again for three weeks and doesn't anticipate an extended layoff.
"Because it's gotten so much better since Monday I think it three days it will be almost 100 percent," Querrey said. "I've got three weeks to get healthy and back on the clay."
Berankis pressured Haas from the start and grabbed the momentum in the eighth game of the opening set when he rallied from consecutive double-faults and survived a break point to take a 5-3 lead. Berankis then broke the German's serve in the final game when Haas hit a drop shot into the net at break point.
Berankis broke Haas in the sixth game of the second set and won it in the ninth game when Haas fought off three match points before sailing a backhand wide to end the match.
"The match started off pretty weird and that didn't give me much confidence," Haas said. "I felt if I could have held serve in the first game, I could have felt him out and maybe it would have been different.
"I gave him the momentum and at times, he played well. It was difficult for me to find a groove. He didn't allow me to find a groove. Credit him on that. I had some chances but I didn't come up with the goods."
Monfils broke Almagro's serve in the fifth and seventh games of the opening set. Serving for the set in the eighth game, Monfils took a 40-love lead, then had consecutive double-faults before closing out the set on Almagro's service return error.
Almagro, ranked 12th, saved three break points in the opening game of the second set before holding his serve. He broke Monfils in the second game and took charge of the match.
Almagro broke Monfils in the eighth game of the third set with a leaping slam off Monfils' attempted lob. Almagro served a love game in the final game.
Isner broke Sock in the final game of the first set, and Sock won the final four points of the second set tiebreaker, including an ace at set point. In the third set, Sock had an ace to take a 3-2 lead in the tiebreaker, but Isner won the final five points to end the match.