The 32-year-old had an impressive debut in Saturday's 1-0 win over Chelsea at Goodison Park and greater things are expected of the midfielder.
"I've known Gareth through the England set-up and I've always rated him really highly," Baines said.
"The City lads on the last international break were saying that they can't believe that they haven't kept him and he doesn't play for them.
"That says enough about his worth for any team he plays in.
"Everyone rates him who he plays with and he has come in and shown what a great asset he is going to be for us.
"We've seen straight away what he can give to the team.
"I'm sure Gaz will tell you that he has not played as much as he would have liked and he has already produced a performance like that.
"If he plays like that most weeks, he is going to add to the team."
Barry believes the victory over Chelsea, the first win of new manager Roberto Martinez's era after three successive draws, can provide a platform.