Newly minted world number one Alexander Zverev suffered a 7-6(5) 6-2 defeat to Italy's Lorenzo Musetti in the second round of the Paris Masters on Wednesday.
Musetti recorded 29 winners and eight aces to secure victory and improve his head-to-head record against the German top seed to 4-2.
Novak Djokovic's qualification hopes for the ATP Finals ended after he was beaten 2-6 6-3 6-3 by Australian world number 83 Rinky Hijikata.