The Argentine international came off the bench to fire in the winning goal against Manchester United last night.
Milner said: "He is not bad is he? He is so sharp when you get him in around the box, him and Carlos (Tevez) together up front.
"We train with them every day. I was speaking to Joleon (Lescott) who says he loves playing against them in training because he knows when he plays against anyone else in the league it is an easier day.
"He is so sharp around the box. His composure and his finish at the end was superb."