WINSTON-SALEM, N.C. (AP) -- Sam Querrey didn't play his best tennis Monday - except when it counted.

Querrey got two key services breaks to beat Spain's Pere Riba 7-6 (7-5), 6-4 in the first round of the Winston-Salem Open, the final tuneup before next week's U.S. Open.

''My year's been pretty average - a lot of two steps forward, one step back,'' Querrey said. ''I had that same problem last year, but I was able to get it going in this tournament. I've played well here in the past, so I'm going to do my best to keep it up.''

The 26-year-old American, who had advanced to the semifinals at Winston-Salem the last two years, got a mini-break to win the first-set tiebreaker. Querrey, ranked 56th, then closed out the match with another service break to advance.

''I didn't think I played great,'' said Querrey, who was ranked as high as 17th in the world in 2011. ''I served pretty well, and hit the big forehand. I did the right things on the big points, but I still need to clean everything up a little bit.''

Querrey will next face childhood friend Steve Johnson, both California natives, in a second-round match Tuesday at the Wake Forest Tennis Center.

Earlier, Belgian qualifier David Goffin defeated defending champion Jurgen Melzer of Austria 6-3, 6-4 Monday to extend his winning streak to 23 consecutive matches.

Goffin won his first ATP Tour title last month in Kitzbuhel, Austria. He lost in the first round to Andy Murray at Wimbledon and then won ATP Challenger Tour events in the Netherlands, Poland and Finland.

''At the beginning of the summer, I didn't expect these results,'' said Goffin, who will face Argentina's Leonardo Mayer in the second round. ''Now, I'm still continuing to win. I'm pretty happy with the way I'm playing at the moment. What can I say?''

After ending the month by winning in Austria, Goffin - whose world ranking has climbed from 106th to 62nd during the run - won back-to-back qualifying matches in straight sets to make the main draw for the Winston-Salem Open.

''The conditions were tough today - the humidity made for a really difficult match,'' said Goffin, who lost to Melzer in four sets in the opening round of the French Open last May. ''After the first set, I think he was really frustrated. He started making some mistakes. I took my chances, and it turned out really well.''

Also, fifth-seeded Guillermo Garcia-Lopez of Spain overcame a tiebreaker loss in the first set to beat Dustin Brown of Germany 6-7 (5-7), 6-2, 6-2.

In other matches, France's Paul-Henri Mathieu overcame a brief rain delay to beat Robby Ginepri of the U.S. 6-3, 7-5; Adrian Mannarino of France downed Bosnia's Damir Dzumhur 6-2, 6-2; Aleksandr Nedovyesov of Kazakhstan beat Marcos Giron of the U.S. 6-4, 6-4; Canada's Frank Dancevic battled to a 7-5, 3-6, 6-2 win over Brazil's Thomaz Bellucci; Poland's Jerzy Janowicz downed Argentina's Carlos Berlocq 6-1, 6-4; Argentina's Federico Delbonis beat Slovakia's Martin Klizan 7-6 (5), 6-4; and Igor Sijsling of the Netherlands defeated Kazakhstan's Andrey Golubev 7-6 (5), 6-3.