The Napoli defender was a top target for Klopp to strengthen his injury-hit defence this winter, but the Serie A giants were asking for as much as £100million to let him go.
Liverpool instead moved for Ben Davies and the loan signing of Ozan Kabak, and latest reports now suggest this has led to tension behind the scenes.
Klopp has surely deserved more backing after bringing so much success to Liverpool in recent years, with not that much in the way of big-money signings made.
Virgil van Dijk and Alisson are the main exceptions there, with elite talents like Mohamed Salah and Sadio Mane signed for fairly cheap in comparison to the kind of money spent even by struggling sides like Arsenal and Manchester United.
Koulibaly could have been a crucial addition to this Liverpool squad due to the injuries to Virgil van Dijk and Joel Matip, but it seems FSG weren’t willing to sanction the deal.
It remains to be seen how much longer Klopp will put up with this as it seems clear his squad will soon need changes after this disappointing season.