A youthful West Ham side ended their Europa League group campaign with a home loss to Dinamo Zagreb.
The Hammers had already won Group H, securing their place in the tournament's last 16 in March and, as a result, David Moyes named a starting XI including five players aged 20 or under.
An inexperienced defence conceded after only three minutes when they backed off Mislav Orsic following a throw-in and he curled the ball into the top corner from the edge of the penalty area.
Sonny Perkins, 17, in his first start for the Hammers, would have become the club's youngest scorer in European competitions but headed over from Harrison Ashby's cross.