KEY BISCAYNE, Florida (AP) ― A big match beckoned for Venus Williams on a court where she first hoisted the championship trophy 15 years ago.

Alas, on Saturday she wasn’t up to any heavy lifting.

The three-time Key Biscayne champion withdrew from the Sony Open because of a lower back injury shortly before her third-round match against fellow American Sloane Stephens.

Williams, seeded 19th, was extended to three sets in the second round Thursday against Kimiko Date-Krumm. She said her back began to bother her Friday, and she decided after warming up that she couldn’t play.

“It’s really disappointing,” she said. “But I have faced disappointments in my life and my career. It’s not the first; probably not the last.”

The cancellation cost the tournament the day’s most appealing match, pitting a rising star against a seven-time Grand Slam champion. The 20-year-old Stephens upset Serena Williams at the Australian Open and is ranked a career-best 16th.

“I’m a little bummed, but I guess a win is a win,” Stephens said. “On to the next round.”

She’ll play defending champion Agnieszka Radwanska on Monday, and could face a rematch against Serena Williams in the semifinals.

With evening traffic on the island in a snarl, five-time champion Serena rode a bicycle to her third-round match and beat Ayumi Morita 6-3, 6-3.