Results on the seventh day of the ATP Finals at London's O2 Arena on Saturday (x denotes seeding): Singles Semi-finals Dominic Thiem (AUT x3) bt Novak Djokovic (SRB x1) 7-5, 6-7 (10/12), 7-6 (7/5) Daniil Medvedev (RUS x4) bt Rafael Nadal (ESP x2) 3-6, 7-6 (7/4), 6-3 Doubles Semi-finals Wesley Koolhof/Nikola Mektic (NED/CRO x5) bt Marcel Granollers/Horacio Zeballos (ESP/ARG x4) 6-3, 6-4 Jurgen Melzer/Edouard Roger-Vasselin (AUT/FRA x7) bt Rajeev Ram/Joe Salisbury (USA/GBR x2) 6-7 (4/7), 6-3, 11-9 afp