Crystal Palace came unstuck in Strasbourg as they slipped to a 2-1 Conference League defeat.
Tyrick Mitchell's first-half goal had put the Eagles on course for a third win from four European matches.
But they were pegged back by Chelsea-bound striker Emanuel Emegha and then sent packing by a first senior goal from teenager Samir El Mourabet.
The Londoners will next face Shelbourne at Tallaght Stadium on 11 December.
With Palace fifth in the Premier League and Strasbourg - managed by ex-Fulham and Hull defender Liam Rosenior - fifth in Ligue 1, this was a showdown between two of the favourites to go all the way to the final in Leipzig next May.
Palace were given an early warning of Strasbourg's threat when Diego Moreira fed El Mourabet, who forced a good save from Dean Henderson at his near post.
Henderson also had to deal with Julio Enciso's shot from the edge of the box before Dutch star Emegha, who has agreed a move to sister club Chelsea at the end of the season, headed narrowly wide.
A tough opening half an hour for the Eagles also saw midfielder Will Hughes forced off with a knee injury.
Yet it was Hughes' replacement, Adam Wharton, who helped create their goal with a long ball towards Jean-Philippe Mateta.
The France striker did brilliantly to hold the ball up before playing Mitchell in behind, with the full-back burying his shot inside the far post.
Palace almost doubled their lead moments later when Strasbourg goalkeeper Mike Penders, also on loan from Chelsea, went walkabout, but Ismaila Sarr's shy at an empty net from 30 yards hit the post and rolled agonisingly across the goal line.
A familiar face came on before half-time, former Palace loanee Ben Chilwell, who is now at Strasbourg on loan from Chelsea as another by-product of Todd Boehly's ownership of both clubs.
Seven minutes after half-time Strasbourg were level, Moreira sending in an inviting cross for Emegha to dispatch from close range.
Palace should have gone back ahead after Penders left himself stranded again, but Wharton's half-volley crashed back off the crossbar.
Emegha almost scored a carbon-copy of his equaliser from Sebastian Nanasi's cross but Chris Richards got back to make a last-ditch tackle.
Yeremy Pino forced a good save from Penders before Strasbourg edged ahead when Encisco's free-kick hit the bar and El Mourabet snaffled the rebound.
Henderson kept Palace in it with a stunning save to deny another Chelsea loanee, Kendry Paez, but they were unable to force an equaliser and stay on six points from their four outings so far.
