Tennis: Mertens and Sabalenka stunned by Schuurs and Gronefeld

Demi Schuurs and Anna-Lena Gronefeld stunned top seeds Elise Mertens and Aryna Sabalenka in the group stage of the WTA Finals. Mertens and Sabalenka suffered a shock 7-5, 1-6, 10-7 defeat by Schuurs and Gronefeld at the end-of-season tournament.