Red Star Belgrade shocked Liverpool with a 2-0 win in the Serbian capital to put a huge dent in Jurgen Klopp's Champions League hopes.
Liverpool brushed aside Red Star at Anfield in their previous Group C encounter with a 4-0 victory, but the Premier League side were off-colour in Belgrade from the off.
Liverpool's start to the game did not go as planned as a brace from Red Star frontman Milan Pavkov saw them 2-0 up inside 23 minutes.
First Pavkov headed the home side ahead from a corner and then doubled the advantage moments later.
James Milner gave the ball away on the halfway line and was severely punished as Pavkov drove home from 25 yards.
Klopp reacted by making two changes at half-time: Gomez and Firmino were brought on in place of Trent Alexander-Arnold and Sturridge.
Despite pressing Red Star in the second half - with Mohamed Salah and Virgil van Dijk going close - the Serbian side held on for a famous win.
The result leaves Liverpool with plenty of work to do in Group C. Klopp's side sit top on six points, but just two points separate them from Red Star in bottom place.
Liverpool have also played a game more than Napoli and PSG, who face off in the late game.
With their final two group games coming against the Italian and French sides, Liverpool can ill-afford another poor result as the race for a top-two finish heats up.
Additional reporting by the Press Association.
