AC Milan fell to their second embarrassing defeat in a row under new coach Pippo Inzaghi when they were thumped by Manchester City in Pittsburgh.
Milan were attempting to bounce back from a 3-0 loss to Greek side Olympiacos, which drew severe criticism in the Italian media.
But instead they looked shell-shocked during a devastating first half hour that saw Manchester City run riot.
Stevan Jovetic, Scott Sinclair, Jesus Navas and Kelechi Iheanacho all found the net for the Premier League champions within 26 minutes, ending the game as a contest and putting Milan into damage control mode.
Former Portsmouth midfielder Sulley Muntari made it 4-1 but at half-time there was little doubt as to the victors.
The second half was delayed for around half an hour due to a thunder storm, giving Inzaghi an extended team talk, but it had little impact.
Jovetic, who is a target for Milan's Serie A rivals Inter and Juventus, added his second for 5-1 and Milan couldn't hit back although Mario Balotelli had a goal disallowed.
Manchester City: Caballero, Clichy, Kolarov (Richards 69), Boyata (Rekik 77), Nastasic, Fernando (Garcia 62), Zuculini (Rodwell 77), Navas (Leigh 77), Jovetic (Guidetti 69), Iheanacho (Huws 62), Sinclair
AC Milan: Agazzi, De Sciglio (Albertazzi 68'), Rami (Mexes 68'), Constant (Abate 46'), Alex (Bonera 46'), Muntari (Saponara 68'), Poli (Essien 46'), Cristante, Honda, Niang, El Shaarawy (Balotelli 46')
Watch Manchester City thrash AC Milan: