DOHA—Serena Williams became the first player through to the semi-finals of the WTA Championships with a 6-2 6-4 win over Russia's Elena Dementieva on Thursday.
The American, who was confirmed as the year-end world number No.1 on Wednesday when her closest rival for the honour Dinara Safina of Russia withdrew injured, made a slow start before overpowering an opponent who served 10 double faults.
Serena has won all three of her Maroon Group matches meaning the three other players are scrapping for second spot, one of whom is sister Venus who must beat Russian Svetlana Kuznetsova later to keep alive her slim hopes of holding on to her title.
"It feels good to be through because I've never really done well in this round-robin format," Serena, who won the tournament in 2001 when it was a conventional knockout draw, said at courtside. "Tomorrow I'm going to sleep all day because I've played every day so far here and I'm really tired."
