Andy Roddick defeated Gilles Muller in straight sets in the first round of the ATP Memphis event.

The top-seeded American, who won in San Jose last week, maintained his momentum with a 7-6 6-4 victory over the qualifier from Luxembourg.

Roddick will meet compatriot Mardy Fish in the second round as he continues his bid for a 25th career ATP Tour title.

Three second round matches were also completed, with third seed Tommy Haas crashing out to fellow German Benjamin Becker despite taking the first set.

Becker hit back to beat the defending champion 3-6 6-2 7-5, ending Haas' 11-match winning streak at this tournament.

Fourth seed Radek Stepanek, who lost to Roddick in the final in San Jose on Sunday, continued his strong form with a 7-6 2-6 7-5 win over Florent Serra.

However, seventh seed Jurgen Melzer lost his second round match 6-3 7-6 to Steve Darcis of Belgium.