Serena Williams secured her place in the WTA Championship final in Istanbul with a comfortable 6-2 6-1 victory against Agnieszka Radwanska.
The American third seed polished off the exhausted Pole in 61 minutes and is now just a win away from her third season-ending tournament title.
The Olympic, Wimbledon and US Open champion, who easily finished top of her group, was looking to take her good form into the semi-final against Radwanska, who came through a three-set marathon with Sara Errani the night before.
In a repeat of the Wimbledon final, the fourth-ranked Radwanska showed plenty of fighting spirit early on, breaking back from an early service loss and reaching 2-2.
But Williams soon punished her leaden-legged opponent's second serve to break it again. And after consolidated by holding with a love game, it was predominantly one way traffic.
Radwanska hung on briefly by holding serve for 1-2 in the second set, but then Williams' controlled aggression completely overwhelmed the 23-year-old by taking each stroke a little earlier, tightening up her drive, and finishing the match as quickly as possible.
"I just told her that it was awesome she played so well and played through another match, after playing a good eight hours. It was really inspiring for me," said Williams.
Williams has now won 47 of her past 49 matches and will finish the year as No. 3 in the world. She will next play French Open champion Maria Sharapova in the final on Sunday.