Karel Novacek of Czechoslovakia upset second-seeded Aaron Krickstein, 6-2, 7-6 (7-4), Thursday in the third round of the BMW Open at Munich, West Germany.
In another upset, Jens Woehrman defeated fifth-seeded Carl-Uwe Steeb, his West German Davis Cup teammate, 7-5, 6-4.
Fourth-seeded Jim Courier, who advanced to the quarterfinals on Wednesday, is the only seeded player left after top-seeded Stefan Edberg and third-seeded Michael Chang were upset.
In another second-round match, Petr Korda of Czechoslovakia defeated Kevin Curren, 7-5, 6-1.
Martina Navratilova breezed past Isabel Cueto of West Germany, 6-2, 6-2, to reach the quarterfinals of the Citizen Cup at Hamburg, West Germany.
In other matches, third-seeded Arantxa Sanchez Vicario of Spain downed 16th-seeded Sylvia Hanika of West Germany, 6-2, 6-1; fifth-seeded Helena Sukova of Czechoslovakia defeated Regina Rajchrtova, also of Czechoslovakia, 7-6, 6-2, and eighth-seeded Judith Wiesner of Austria beat Wiltrud Probst of West Germany, 6-3, 6-2.
Marc Rosset of Switzerland defeated third-seeded Emilio Sanchez Vicario of Spain, 4-6, 6-4, 6-4, and second-seeded Andres Gomez of Ecuador defeated Diego Perez of Uruguay, 3-6, 7-6 (7-4), 6-0, in the second round of a Grand Prix tournament at Madrid.