KEY BISCAYNE, Florida, Mar 24 (AP/UNB) - Venus Williams took a big step in her comeback Friday when she defeated reigning Wimbledon champion Petra Kvitova 6-4, 4-6, 6-0 in the second round of the Sony Ericsson Open.

Williams is playing in her first tournament since she withdrew from the U.S. Open in August after being diagnosed with a fatigue-causing autoimmune disease.

She showed plenty of staying power against the third-seeded Kvitova, taking charge in the final set. When Kvitova pushed a weary forehand wide on the final point after nearly 2{ hours, Williams trotted to the net with a grin and raised fist.

A former No. 1 and seven-time Grand Slam singles champion, Williams is ranked No. 134 and needed a wild card to enter the tournament, which she has won three times.