Tennis Roundup : Muster Continues to Roll, Surprises Mecir, 6-4, 7-6

Thomas Muster of Austria upset top-seeded Miloslav Mecir of Czechoslovakia, 6-4, 7-6, in the third round of a $350,000 Grand Prix tennis tournament Thursday at Stuttgart, West Germany.

In other matches, ninth-seeded Guillermo Perez-Roldan of Argentina eliminated Emilio Sanchez of Spain, 6-4, 6-3; second-seeded Andre Agassi defeated Tomas Smid of Czechoslovakia, 7-5, 6-2, and Ronald Agenor of Haiti surprised third-seeded Brad Gilbert, 2-6, 6-3, 6-4.

Also, Yannick Noah of France beat Eduardo Bengoechea of Argentina, 6-3, 6-1; Andres Gomez of Ecuador ousted Kent Carlsson of Sweden, 6-4, 6-7, 7-5; Henri Leconte of France downed Martin Jaite of Argentina, 6-3, 6-2, and Jonas Svensson of Sweden routed Sergio Casal of Spain, 6-2, 6-1.

Top-seeded Joakim Nystrom was extended to three sets again but fared better than two other seeded players in the Swedish Open.

Nystrom, the defending champion, overcame Niklas Kroon, also of Sweden, 3-6, 6-4, 6-1, in the third round at Bastad, Sweden.

While Nystrom was escaping, Paolo Cane of Italy upset third-seeded Jan Gunnarsson of Sweden, 7-6, 6-1, and Christian Bergstrom, another Swede, knocked off fifth-seeded Horst Skoff of Austria, also 7-6, 6-1.

In other matches, No. 7-seeded Marcellino Filipino of Uruguay defeated Ronnie Bathman of Sweden, 6-2, 6-7, 6-1; No. 8 Udo Riglewski of West Germany downed Claudio Pistolesi of Italy, 7-6, 6-1; Fernando Luna of Spain beat Nicklas Kulti of Sweden, 6-4, 6-2, and Francesco Cancellotti of Italy eliminated Alberto Tous of Spain, 6-3, 6-1.

Second-seeded Lori McNeil overcame five service breaks and defeated 15-year-old Amy Frazier, 6-3, 6-4, in the second round of the $200,000 Virginia Slims of Newport, R.I., tournament.

Lea Antonoplis upset seventh-seeded Gretchen Magers, 6-4, 6-7, 6-3, and Wendy White beat Carol Christian, 6-3, 7-6.