AEK Athens eliminated Scottish champion Celtic in the third round of Champions League qualifying on Tuesday.
The three other former European champions in action all advanced as Benfica, Ajax and Red Star Belgrade won their games.
AEK beat Celtic 2-1 in Greece thanks to goals from Rodrigo Galo and Marko Livaja to secure a 3-2 win on aggregate. Scott Sinclair responded with a goal for Celtic, the 1967 European Cup winner.
Celtic reached the Champions League group stage in the last two seasons, but the defeat continues a difficult start to the season for Brendan Rodgers' team following a 1-0 loss to Hearts in the Scottish league on Saturday.
Portuguese club Benfica earned a 2-1 aggregate win over Turkish team Fenerbahce, while Dutch league runner-up Ajax cruised past Belgium's Standard Liege, winning 3-0 on Tuesday for a 5-2 aggregate victory.
Serbia's Red Star Belgrade needed extra time to defeat Spartak Trnava 3-2 over two legs thanks to a 98th-minute goal from Nemanja Radonjic.
There was no post-World Cup buzz about Spartak Moscow, which lost 3-2 to Greece's PAOK on aggregate after a red card for striker Luiz Adriano.
Dynamo Kiev, Salzburg, Dinamo Zagreb, Vidi and BATE Borisov also advanced to the last stage of qualifying. Tuesday's losing teams drop into the Europa League qualifying playoff round.