Martina Navratilova was pushed to the limits Sunday by young Soviet Natalia Zvereva before rallying to win the $300,000 New England Virginia Slims championship. The 32-year-old Navratilova took her 137th career singles title and prevented the 17-year-old Russian from capturing her first tour event with a 6-7, (4-7), 6-4, 6-3 victory.