Milner was playing for the Reds in their semi-final first-leg clash at the Nou Camp and was tasked with keeping the Argentine forward quiet.
He managed to do that in the first half in Spain but on one occasion, left the Barca hero livid after clattering into him with a late challenge on the touchline.
The pair were seem squaring up on the Nou Camp pitch, and Messi continued their alteration in the tunnel at half-time and insulted his rival in Spanish – unaware that the former England international can speak the language too.
“He wasn’t happy,” Milner told the Mail on Sunday . ‘He was giving me plenty in Spanish going down the tunnel at half-time as well.
“He was calling me ‘burro’. It translates as donkey but I think it’s also used in Spanish football as a general term for someone who goes around kicking people.
“I asked him if he was all right, but he wasn’t having it. I don’t think he realised I understood his Spanish. He said: ‘That foul you did, that’s because I nutmegged you’.
“I left him to it at that point and went into the changing room.”
Messi came out for the second-half keen to impress and certainly did that, scoring a stunning late brace to seal a 3-0 first-leg victory.
And Milner has revealed just how hard it is to play against a player of Messi’s ability.
“Look, I’ve only got admiration for him. He has earned the right to say what he wants,” he added.
“The stuff he did in that game, stuff he has done his whole career, it makes him tough to play against.
“If you try and stop him, you can’t be scared of being made to look foolish. I’ve done it.
“I’ve been nutmegged by him and it has been viewed a million times. I wasn’t the first and I won’t be the last. He’s an incredible player.”
Liverpool went on to mount a remarkable second-leg comeback, securing a 4-0 win at Anfield to book a final date with English rivals Tottenham .