VIDEO: Re-live Liverpool's 2-0 loss at Red Star
Manager Jurgen Klopp said Liverpool struggled to "find their mojo" as two early goals from Milan Pavkov gave Red Star Belgrade a shock victory in their Champions League group-stage encounter
could have taken Liverpool three points clear at the top of Group C but they dropped to second following Napoli's draw with Paris St-Germain in Italy.
Forward Pavkov headed his side into the lead after 21 minutes and fired home a powerful effort to make it 2-0 shortly afterwards.
"I saw a few games like this already and it is really difficult to find your mojo," Klopp said.
"We made life a bit too easy. I don't say it is already serious if you lose twice but we have to make sure it will happen again.
"We had a lot of moments when we could get in control of the game and we didn't do it, we just made the wrong decision."
Red Star dominated the first half and came close through Vujadin Savic and El Fardou Ben Nabouhane before opening goal.
Liverpool's Daniel Sturridge squandered a great chance from six yards out in the 17th minute.
Klopp's side had more than 80% of the possession and hit the woodwork twice in the second half but could not score as Red Star recorded their 10th clean sheet in their 15 home games in Europe.
Watch highlights of the match below;
UEFA Champions League Results;
Monaco 0 - 4 Club Brugge
Atletico Madrid 2 - 0 Borussia Dortmund
Inter 1 - 1 Barcelona
Tottenham Hotspur 2 - 1 PSV Eindhoven
FK Crvena Zvezda 2 - 0 Liverpool
Napoli 1 - 1 Paris Saint Germain
FC Porto 4 - 1 Lokomotiv Moscow
Schalke 04 2 - 0 Galatasaray