Michael Kures of Czechoslovakia lost a 10-minute argument over a line call, then upset third-seeded Brad Gilbert, 7-5, 4-6, 7-6, Thursday in the $415,000 U.S. Pro Tennis Championships at Brookline, Mass.
In another upset, Lawson Duncan knocked off fourth-seeded Guillermo Perez-Roldan of Argentina, 6-1, 6-4.
Kures objected to a belated line call that gave Gilbert a 3-2 lead in the tiebreaker. Umpire Frank Hammond allowed the decision to stand, but Kures rallied to win, 7-4.
Fifth-seeded Aaron Krickstein defeated 12th-seeded Richey Reneberg, 7-5, 6-1, and eighth-seeded Tom Muster of Australia beat Jim Courier, 6-2, 6-2.
In her first match since winning Wimbledon, Steffi Graf had 14 aces and needed just 42 minutes to defeat Nicole Provis of Australia, 6-2, 6-3, in the Gunze World tournament at Yokohama, Japan.
In another match, Mary Joe Fernandez beat Katerina Maleeva of Bulgaria, 7-6, 6-1.
In men's singles, Anders Jarryd of Sweden defeated David Pate, 6-3, 6-4.