Qualifiers Wayne Ferreira and Chuck Adams beat seeded opponents at the U.S. Pro Indoor tournament in Philadelphia yesterday.

Ferreira, from South Africa, ousted No. 8 Tim Mayotte, 6-4, 6-2, who had had a bye into the second round. Adams surprised 10th-seeded Derrick Rostagno, 7-5, 6-3.

Pete Sampras, seeded No. 2 behind Ivan Lendl, began defense of his title with a 6-2, 7-5 second-round victory over Milan Srejber.

Mayotte, twice champion and twice runner-up in the U.S. Pro Indoor, couldn't fend off Ferreira, ranked 147th, after he broke the American for a 5-4 first-set lead on a passing shot down the line. Ferreira won the last four games in the second set.

Kevin Curren and Jim Grabb also upset seeded opponents. Curren defeated No. 5 seed Jay Berger, 6-1, 6-2. Grabb put out No. 6 Jim Courier, 6-2, 6-4. Grabb, a finalist in last year's Washington tournament, gained a 3-1 lead in the second set and won from 5-4 on an ace down the center.

Belgium: Stefan Edberg swept Magnus Gustafsson, 6-0, 6-4, in the opening round of the Donnay Indoor in Brussels. Goran Prpic overtook Henri Leconte, 6-7 (4-7), 6-4, 6-2. Ronald Agenor eliminated 1990 finalist Carl-Uwe Steeb, 6-2, 7-5.

Boris Becker opens defense of his title today against Alexander Volkov. Edberg is seeking to close the gap on Becker, who took over his No. 1 spot in the ATP rankings. This tournament has 180 points at stake; Becker's lead in the world standings over Edberg is 133.

Becker asked organizers for a wild-card entry into the tournament, changing his plans to pass up the event. Not playing would have automatically meant relinquishing his top ranking to Edberg.

Virginia Slims: On the Chicago tour stop, Amy Frazier outlasted Leila Meskhi in a first-round battle of baseliners, 6-2, 6-7 (5-7), 6-4. Meskhi, winner of Sunday's Fernleaf tournament in New Zealand, spent 17 hours in the air, then went at Frazier for two hours.

Fifth seed Zina Garrison and No. 6 Helena Sukova advanced in straight sets.

Austrian Indoor: No. 1 seed Manuela Maleeva-Fragniere and No. 2 Barbara Paulus breezed through the first round in Linz.