Top-seeded Ivan Lendl was given quite a battle before downing Mexican teen-ager Leonardo Lavalle, 6-4, 0-6, 6-4, 6-2, in the second round of the $1.5 million Australian Open.

The U.S. Open champion, 25, was fully extended by the left-handed junior Wimbledon champion, 18, who served superbly through 2 1/2 sets and hit some exquisite ground strokes.

Lendl, playing his first match in the grass-court tournament after being given a first-round bye, along with all the other men's seeds, looked ill at ease for a long period before elevating his game. He is bidding to win his first Australian title.

Lendl's third-round opponent will be 1980 Australian Open champion Brian Teacher or Ben Testerman, a 1984 semifinalist.

A first-round men's singles produced a surprise second-round opponent for No. 2-seed John McEnroe. McEnroe had been expected to meet Bill Scanlon, but the Texan was beaten, 4-6, 7-6, 6-0, 6-2, 8-6, by South African Danie Visser.

Chris Evert Lloyd opened defense of her women's title by defeating Ros Fairbank, 6-1, 6-2. No. 2 seed Martina Navratilova, No. 3 Hana Mandlikova and No. 4 Pam Shriver won easy matches.