West Ham endured a chastening 2-1 defeat by Slovenian minnows NK Domzale in their Europa League third-round first-leg qualifier at Stozice Stadium.
Even with England striker Andy Carroll at the spearhead of a strong line-up, the Hammers came off second best against a club who were making their first appearance in Europe.
Slavin Bilic, who watched from the stands as he served the second game of his two-match touchline ban, saw Mark Noble pounce from the spot while the superb Matic Crnic scored both of Domzale’s goals.
The rivals meet again in next Thursday’s second leg at the Olympic Stadium where West Ham, who only avoided a 3-1 final scoreline when Adrian made a brilliant late double save, will demand a substantial improvement.
Bilic gave debuts to Havard Nordtveit and Sofiane Feghouli, but any pre-season optimism evaporated when they fell behind inside the opening 11 minutes.