Serena Williams admits she was second best against Caroline Wozniacki

Serena Williams has admitted that she was second best in her WTA Tour Finals contest against Caroline Wozniacki, despite defeating the Dane 2-6 6-3 7[8]-6[6].

The American confessed that she felt for her opponent after the game, adding that it is Wozniacki who deserves to be in the final.

"Caroline played a great match, it was really difficult today. I feel so bad," BBC Sport quotes the 33-year-old as saying.

"She's the only one undefeated [after the group stages] in this tournament and she deserved to win."

Williams will take on Simona Halep in the final in Singapore.