The former Red was delighted when Liverpool swooped to sign Coutinho in January.
Warnock told LFC TV: "I think since he's come in, he's adapted well to the game and the style Liverpool want to play.
"I thought he was a very good player and kept my eye on him.
"He seems to be a player the fans like as well and they've taken to him. Scoring quite early on helped him, but he's been impressive."