Foster has only just recovered from long-term injury.
Assessing the England scene and with Hart back in form after being dropped by City boss Manuel Pellegrini earlier this season, Foster told Albion's official website: "You've got to look at Joe.
"He's come back into the Man City team and he looks as fresh as a daisy.
"He is a huge asset for the England team, and one of the best keepers I've ever trained with.
"I think he should start in the World Cup. As long as he keeps his performances up high then he will be a huge benefit for us in Brazil.
"Don't get me wrong, I want to play, but I've got to be realistic."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball