Bartoli replaces injured Serena Williams at Sony Ericsson

MADRID, Spain -- Serena Williams withdrew from the Sony
Ericsson Championships on Thursday after being forced to retire
from a match the previous day against Anna Chakvetadze with a left
knee injury.

The fifth-ranked Williams had lost the first set 6-4 in
Wednesday's match before having an MRI scan. It's the same knee
that underwent surgery in 2003 and also forced her to miss 10
tournaments last year.

"I felt it maybe a little bit yesterday, but it wasn't too
intense," Williams said. "I had a really short practice
yesterday, and the day before I had a short practice. It's really

Wimbledon finalist Marion Bartoli replaced Williams and was to
play defending champion Justine Henin later Thursday. Bartoli
assumed Williams' one loss for the remainder of the round-robin

Williams, who had strips of material on both knees, was treated
by a doctor before the ninth game at 4-4. The 2001 champion played
on, but the seventh-ranked Russian had little trouble closing it

"I was hoping that [the bandages] would work out for me,"
Williams said.

Williams, who had reached the Sony Ericsson Championships final
in her three previous appearances, said defending her Australian
Open title in January will be her focus to return.

This has been another frustrating year for Williams with

After winning her eighth career Grand Slam at the Australian
Open, Williams has withdrawn from nine tournaments due to illness,
a groin injury, a thumb sprain and an adductor strain.