Napoli's excellent start to the new season ran aground in Eindhoven where they were beaten 3-0 by PSV in the Europa League Group F.
Walter Mazzarri's men went into the game unbeaten in seven but were behind after seven minutes from a Jeremain Lens strike, and Dries Mertens and Marcelo added further goals for the Dutch side.
Dnipro, who had beaten PSV in their opening game, claimed their second straight win as they came from behind twice to beat AIK 3-2 in Sweden.
Goals from Helgi Danielsson and Henok Goitom for the hosts were cancelled out by efforts from Nikola Kalinic and Vitaly Mandzyk before Evhen Seleznyov struck to seal the points seven minutes from time.
Reigning champions Atletico Madrid needed an injury time winner from Cristian Rodriguez to extend their run of wins to eight with a 1-0 triumph over Viktoria Plzen in Spain. Also in Group B, Omer Damari struck an injury time equaliser for Hapoel Tel Aviv in a 1-1 draw at Portuguese side Academica, who led through a Salim Cisse effort.
Ligue 1 leaders Marseille returned to form in emphatic fashion after the weekend's humiliating defeat to Valenciennes as they beat Cypriots AEL 5-1 in Group C. Edwin Ouon put the visitors in front but goals from Rod Fanni, Michel Mendes, Andre Gignac and two for Loic Remy saw Marseille home.
There were six more goals in the other Group C tie as Fenerbahce won 4-2 at Borussia Monchengladbach. Luuk De Jong put the hosts in front but Cristian Baroni hit two and further goals were added by Raul Meireles and Dirk Kuyt, with Igor De Camargo grabbing the Germans' second.
Club Brugge beat Maritimo 2-0 with goals from Carlos Bacca and Bjorn Vleminckx.
A late own goal from Ragnar Sigurdsson gave Steaua Bucharest a 1-0 win over FC Copenhagen in Group E, while Jo-Inge Berget and Daniel Chima scored in Molde's 2-0 home win over Stuttgart.