Serena Williams is guaranteed to finish the year as the top ranked women's tennis player, with her rival Dinara Safina pulling out of the year ending WTA Championships with injury in Doha.
Safina lasted just two games against Serbia's Jelena Jankovic in her first match at the season-ending showpiece that features the top eight players.
It means Williams will end the year in the number one spot for the first time since 2002.
She won her opening match against sister Venus 5-7 6-4 7-6 in a near three-hour contest that finished after midnight.
