Steffi Graf struggled before ousting Lori McNeil Thursday in the third round of the Player's Challenge Canadian Open at Montreal.
Graf won, 7-5, 6-3, the first time in five meetings she had beaten McNeil in straight sets.
Gabriela Sabatini of Argentina and Katerina Maleeva of Bulgaria, seeded second and third behind Graf, had much easier times advancing.
Sabatini lost the opening game to Raffaella Reggi of Italy before winning the next 12 for a 6-1, 6-0 win, and Maleeva defeated New Zealand's Julie Richardson, 6-0, 6-0, at the hardcourt event at Jarry Stadium.
Fourth-seeded Manuela Maleeva, Katerina's older sister, defeated Helen Kelesi of Canada, 6-3, 2-6, 6-3, and fifth-seeded Natalia Zvereva of the Soviet Union disposed of Britain's Jo Durie, 6-4, 6-2.
Martin Wostenholme launched a pair of decisive passing shots to gain an 11th game service break to take a 7-5, 6-1 victory over Paul Annacone in second-round play at the U.S. Pro Tennis Championships Thursday at Brookline, Mass.
"I wasn't very sharp," said Annancone. "When I came to the net at five-all, he hit a couple of good passing shots to break my service and I never could get back into the match."
Of the 27-year-old Wostenholme, Annacone said: "He runs real well and returns shots that you'd think were unreturnable."
David Wheaton withdrew after aggravating a hip injury suffered last week in Toronto.
Top-seeded Boris Becker and local favorites Thomas Muster and Horst Skoff scored victories and advanced to the quarterfinals of the Austrian Open in Kitzbuehel, Austria.
Becker played unevenly but managed to oust Sweden's David Engel, 6-4, 4-6, 6-0.
Muster, seeded fourth, beat Marian Vajda of Czechoslovakia, 6-3, 6-0, and will face Skoff in the quarterfinals. The sixth-seeded Skoff beat Spain's Tomas Carbonell, 6-2, 6-0.
A third Austrian, 10th-seeded Anton Antonitsch, was beaten by Czechoslovakia's Karel Novacek, 6-3, 6-7 (7-4), 6-4.