Mats Wilander, with his second major upset in two days, and Martina Navratilova, with her second victory over Chris Evert Lloyd in eight days, won yesterday in the last major pro tennis tournaments before the U.S. Open begins next week.

Wilander defeated John McEnroe, 6-4, 6-3, in the final of the $375,000 Association of Tennis Professionals Championships in Mason, Ohio. Wilander, 19 today, upset second-ranked Ivan Lendl in the semifinals.

"I can't play better tennis than I did today," Wilander said. "I didn't think I had a chance to win, not after last week (at Montreal) when I lost in the first round."

Navratilova played a third set for the sixth time this year. Her 6-4, 4-6, 6-1 victory in the $250,000 Player's Challenge in Toronto gave her four victories over Evert this season. And she has won seven of their last eight matches.

Navratilova has won 59 of her past 60 matches and 11 of 12 tournaments.

McEnroe, the top-ranked player in the world, said he was a little surprised by Wilander, not known as a great hard-court player.

"That's the best I've seen him play on this type of court," McEnroe said. "If this is an indication of things to come, he's going to be tough."

Each player held serve until the fifth game of the first set, when McEnroe broke Wilander to take a 3-2 lead. Wilander broke McEnroe in the eighth game and again in the 10th to win the set.

Each player held serve through seven games of the second set. Wilander broke McEnroe to take a 5-3 lead and held service to win the match.

The victory was worth $48,000 to Wilander. McEnroe collected $24,000.

"Martina played a little different than she did our last three matches," said Evert.

"In the last three she played great and didn't make any errors. This time she was definitely beatable.

"If I was playing a little better, I would have closed in more in the first set. I was disappointed. I felt with the way she was playing, I could have beaten her. She just produced good shots when she needed to." Evert had won only 10 games in her three previous matches with Navratilova.

"I thought (Evert) played really well today," said Navratilova. "It was the best I've seen her play in a while, even better than when she beat me in the Australian Open (in 1982, Evert's last victory over Navratilova). She can play better than she did today. But I can play a whole lot better."

For 87 minutes' work, Navratilova took home the $42,500 first prize.

Navratilova took a 4-0 lead to assume control of the third set with aggressive play at the net. She limited the second-ranked Evert to four points in that span.