United were beaten by their hosts PSV Eindhoven in a match that was overshadowed by an injury to United full-back Luke Shaw, who suffered a double leg fracture.
City failed to convert their early league form into Europe as Juventus recovered from 1-0 behind to claim a smash-and-grab victory at Eastlands.
Later tonight, Arsenal, Chelsea and defending champions Barcelona will all be in action.
Arsenal begin their Group F campaign away to Dinamo Zagreb while Chelsea will be hoping to kick-start their season when they host Maccabi Tel Aviv at Stamford Bridge.
Barca's title defence begins with a trip to Italy to face their Group E rivals, AS Roma.
All of those matches will kick-off at 19:45.
