Serena speaks of depression

Serena Williams has revealed she has battled feelings of depression during her long injury lay-off that has seen her sidelined since claiming her 13th Grand Slam title at Wimbledon last July.

The 29-year-old is recovering from an operation to remove a blood clot found in her lung a fortnight ago. Williams had developed a haematoma from a pulmonary embolism, stemming from an incident when she cut her foot on broken glass in a Munich restaurant last July.

"I definitely have not been happy," Williams said. "Especially when I had that second (foot) surgery, I was definitely depressed. I cried all the time. I was miserable to be around."

The American, who has slipped to world number 11 in her absence from the WTA Tour, is unlikely to return before the summer and admitted the time spent on the sidelines had taken an emotional toll.

Williams said that a part of her lung had "died" from the pulmonary embolism and that she remained on blood thinning medication.

She added that she is due to have further scans in three weeks to see if the clots are melting and with her health issues still not resolved is understandably coy about a possible return date.

"I don't know what's realistic. I really don't know. I haven't put a date on it yet," she told USA Today. "I just want to make sure I can breathe when I'm out there."

Williams is confident, however, that when she does return to the court she will be able to recapture the form that has made her arguably the best player of her generation.

"I know how to play tennis. I've been doing it for a long time - longer than I can say. So I figure that will work out," she added.

"I always think I'm going to play again and I'm going to be faster, I'm going to be better, I'm going to be smarter, wiser."