Iga Swiatek earned a straight-sets win against Madison Keys on the first day of the WTA Finals.

The world No 2 put in an assured display to record a 6-1 6-2 victory against the American in their Serena Williams Group round-robin clash.

Swiatek took 61 minutes to wrap up victory and won 12 out of the 15 games played, managing to convert five break points.

The contest was Keys' first since being defeated in the first round of the US Open in August, with a wrist injury having kept her out of action.

Reflecting on the match, Swiatek said: "Kind of [happy] with everything. Mostly my serve and overall focus.

"I was in the zone from the beginning to the end, and I really wanted to keep it that way."

Elena Rybakina also enjoyed a straight-sets win over Amanda Anisimova.

The world No 6 completed a 6-3 6-1 victory in just under an hour, serving seven aces and converting four break points.

The Stefanie Graf Group begins on Sunday, with world No 1 Aryna Sabalenka taking on Jasmine Paolini, and Coco Gauff facing Jessica Pegula in an all-American clash.

Watch the WTA Tour Finals and the ATP Paris Masters live this weekend on Sky Sports or stream with NOW.