Milner has been rewarded for an excellent first season at Villa Park by being named in the England squad for the World Cup qualifiers with Kazakhstan and Andorra as a replacement for the injured Michael Carrick.
The winger has been one of Villa's most consistent performers since making the switch from Newcastle in August and helped them qualify for the revamped Europa League.
Carew, who finished as Villa's leading scorer with 15 goals, said: "James has been fantastic for us. He has been one of our best players this last season.
"He is right up there with Gabriel Agbonlahor and Ashley Young when it comes to importance in the team.
"He has definitely proved he is worth the price tag, maybe even more, not only in the games but in the way he trains.
"He has been in the top three in training every day. He never has a bad day. He is always good for us. He gives everything all the time. His commitment is fantastic."