Liverpool boss Jurgen Klopp allegedly 'angered' Atletico Madrid with accusations of diving during their Champions League clash on Tuesday night.
An early goal from Saul Niguez condemned Liverpool to a rare defeat, putting the reigning European champions under pressure ahead of next month's reverse fixture at Anfield.
After the game, Klopp claimed that he had substituted Sadio Mane at half time as he feared that the Senegal international would be handed a second yellow card, suggesting that Atletico would attempt to get the winger dismissed.
According to ESPN, the comments annoyed the Spanish giants, who feel that Klopp should have been 'gracious' in defeat.
Given the short margin of victory ahead of the second leg, Klopp also felt that Atletico 'over-celebrated' at the full-time whistle.
Liverpool play host to Diego Simeone's side on March 11.
BFC Dynamo 
Monaco 
FC Kaiserslautern 
Bayer Leverkusen 
AC Milan 
Salernitana 
Lyon 
Paris Saint Germain 
Real Madrid 
Betis 
Celta Vigo 
Valencia 
Empoli 
Roma 
Frosinone 
Udinese 
Lazio 
Sassuolo 
Napoli 
Lecce 
Verona 
Inter 
FC Porto 
Sporting CP 
Amorebieta 
Espanyol 
Sevilla 
Barcelona 
Olympiacos Piraeus 
Fiorentina 
Borussia Dortmund 
Atalanta 
Cartagena 
Gibraltar 
Scotland 
Croatia 
North Macedonia 
Albania 
Liechtenstein 
England 
Bosnia & Herzegovina 
Germany 
Ukraine 
Slovenia 
Armenia 
Switzerland 
Estonia 
Romania 
Bulgaria 
Austria 
Serbia 
Portugal 
Finland 
Rep. Of Ireland 
Hungary