Aston Villa made a poor start to a first European campaign in 13 years as some appalling defending allowed Legia Warsaw to get the better of them in their Europa Conference League group opener.
Returning to continental competition thanks to a stunning run of form in the second half of last season, the former European champions looked good going forward but continually gave Legia a leg up at the other end.
The tone was set after just three minutes as Pawel Wszolek was allowed to get ahead of his marker to slot a low cross home before Jhon Duran made amends by heading home after Nicolo Zaniolo's shot had been pushed on to the bar by home keeper Kacper Tobiasz.
Again, though, Legia were invited on, with Ernest Muci left alone to charge in, latch on to Wzsolek's cross and fire home.
Lucas Digne's deflected strike cancelled that out but the defensive horror show from the Premier League side continued after the break as Legia were gifted possession and Muti given all the room he needed to fire a superb low shot inside the far bottom corner.
This time Villa had no response.
In fact, they could easily have lost by more had Emiliano Martinez not pulled off some fine saves, including to deny Bartosz Slisz before Calum Chambers cleared Marc Gual's follow up off the line.
Jacob Ramsey - making his return from injury - had a great chance to nick a point, but lashed a shot wide before Leon Bailey fires into the side-netting in added time.
Villa's next European game is on 5 October when they host Zrinjski Mostar, who beat Alkmaar 4-3 in Group E's other game on Thursday.
Villa's surge to European football last season was completed as another side in claret and blue were on the final charge to their own moment of continental glory.
West Ham's victory in the Europa Conference League serves as an enticement for what is possible if you take this competition - ostensibly Europe's third-tier event - seriously.
And if anyone knows the joys European success can bring to a club unlikely to challenge for league titles domestically it is Villa boss Unai Emery, who led Sevilla to Europa League triumphs three seasons running before subsequently winning it with Villarreal.
The Spaniard will be concerned, though, at just how shaky Villa looked at the back in this - something that has already cost them some heavy defeats in away games of their league campaign this season.
Five changes were made to the side that beat Crystal Palace at the weekend but only Duran furthered his cause for inclusion.
At the other end, Chambers and debutant Clement Lenglet looked nervy and were slow to react to the threats Legia posed on the break.
Digne has been a regular this season and scored on the night, but his vulnerability at left-back suggests Alex Moreno could make a return to the side after recovering from injury.
It was not a game midfielder Youri Tielemans will add to his scrapbook either.
In broader terms, what the result demonstrates, as West Ham found last year, is that unfamiliar sides from smaller leagues in Europe are not to be underestimated. Legia were disciplined, savvy and packed a potent punch going forward.
It could be argued they got a bit lucky when Patryk Kun saw only yellow for a studs-up high tackle on Leon Bailey 20 minutes into the game, but having survived that they were superb.
This group may have looked like a breeze to some, but Villa now have work to do to prove their European credentials again.