West Ham drew a blank in the Black Forest as they slipped to a 1-0 defeat in the first leg of their Europa League last-16 meeting with Freiburg.
Jarrod Bowen and Lucas Paqueta missed golden opportunities to give the Hammers a lead to take back to the London Stadium next week.
But instead they will have to come from behind after they were hit by a late sucker punch from Freiburg substitute Michael Gregoritsch.
They were also denied what looked a clear penalty for handball in stoppage time after the referee refused to change his decision despite checking the pitchside monitor.
Nine months to the day since they lifted the Europa Conference League trophy in Prague, West Ham were back on their continental travels, and against familiar opponents.
Freiburg were the visitors to east London for the final group game just 84 days ago when a 2-0 win secured top spot for the Hammers.
West Ham also won 2-1 on their previous visit to south-west Germany in October, and travelled buoyed by back-to-back Premier League wins following a below-par start to the year.
Boss David Moyes, keen on another strong run in Europe, named his strongest line-up with cup goalkeeper Lukasz Fabianski replacing Alphonse Areola in the only change from Saturday’s victory at Everton.
West Ham were, as usual, happy to let their opponents have the ball but Freiburg gave them a scare when Roland Sallai’s through-ball split their defence.
Fortunately, Lucas Holer hit his shot into the ground and straight at Fabianski.
Moments later Bowen made a horrible mess of West Ham’s only chance of the first half.
The forward, who has not scored in Europe since his famous last-minute winner against Fiorentina in the Czech capital, peeled away at the far post to meet a Mohammed Kudus cross but badly fluffed his volley.
At the start of the second half Ghana winger Kudus cut inside Freiburg full-back only to curl his shot straight at keeper Noah Atubolu.
Bowen then scampered down the right wing and crossed for Paqueta, who also scuffed a volley wide.
A James Ward-Prowse corner should have been converted by Konstantinos Mavropanos but the centre-half’s header grazed the far post.
Paqueta then met another superb cross from Kudus but the finish, a simple header, again did not match the quality of the delivery, before Atubolu did well to tip Bowen’s curler wide.
Tomas Soucek also fired straight at Atubolu and Bowen just missed Aaron Cresswell’s cross before Freiburg struck.
A sloppy pass from Edson Alvarez gifted them possession and when Sallai took aim from the edge of the area, his wayward shot was tapped in by Gregoritsch.
Four minutes into stoppage time the ball struck the arm of Freiburg youngster Noah Weisshaupt in the area but after a long VAR check, referee Alejandro Hernandez checked the replay and stuck to his guns.
