Serena Williams unlikely to return at the Pan Pacific Open.

Women's world No. 1 Serena Williams is unlikely to make her return to tennis at the WTA Pan Pacific Open in Tokyo, a source with knowledge of the situation tells ESPN.

Williams, who's not playing in the U.S. Open due to a cut on her right foot that required surgery, has had a protective boot removed. She has said she was targeting the Pan Pacific Open, which begins Sept. 26, for her return to action.

Williams hasn't played competitively since winning Wimbledon. She was reportedly hurt by a broken glass at a restaurant while she was in Munich in July. She had surgery on July 15.

Williams said doctors advised her not to play the U.S. Open so that her foot can heal, and she called missing the tournament "one of the most devastating moments of my career." The top-ranked Williams has won three titles at Flushing Meadows, part of her 13 Grand Slam singles championships.

Kim Clijsters said she saw Williams' foot lacerations and "it's not something that she's making up or that it's a small cut or anything."

After she was hurt, Williams played in an exhibition match against Clijsters that drew a tennis-record crowd of 35,681 in Brussels on July 8.

Clijsters said Monday that Williams actually had cuts on both feet, but she doesn't recall whether they were on the top or bottom.

It was against Clijsters in last year's Open semifinals that Williams went on a tirade against a line judge over a foot-fault call. That led to Williams losing the match and receiving a record fine.