The 32-year-old has scored just seven goals in 57 appearances for his country since making his debut in 1999.
He found the net only five times in 40 matches for Villa, and once in nine England matches this season.
Carew, ironically, was the man who restricted Heskey's appearances as his form saw him hit 17 goals.
However, the Norway international believes until you play alongside Heskey you do not really appreciate his worth.
"You know what Emile's about, how much he means to the team and how much he means for the other striker," said Carew.
"In the role he plays for the team, he is fantastic - holding up the ball, supporting the second striker, creating the space.
"He will do so much for you as a striker, it is amazing. I know he gets some criticism every now and again but I just think that is not fair because of the role he is playing.
"He is one of the strongest there in his role. That is why he is also playing so many games for the national team - because they know he is important.
"In the few games I have played with him I have noticed his presence around when he is playing. Gabby (Agbonlahor) has been enjoying it and I've been enjoying it as well.
"Together with another striker he can be very important and (England coach) Fabio Capello knows that."
Carew defended Heskey's goals-to-games ratio by stressing it was often the unselfish work the player did which resulted in other team-mates benefiting.
"With his role on the pitch he will still make the team score goals and he will create big chances for the other striker," the striker told the club's official website, www.avfc.co.uk.
"That is what the trainer and the manager see in the player as well, because he creates so much for the rest of the team.
"He lifts the team, he holds the ball and he creates so many chances for the players around.
"So with him around, the second striker will probably score more goals and one or two of the midfielders will score more goals."