Foster insists Rashford is overrated and suffers from a poor attitude.
"Marcus Rashford...," he began on his Cycling GK podcast. "There's so many people that talk about him that say 'on his day, on his day'.
"His day is once every 10 games. Genuinely, it's once every 10 games and you can't have a luxury player in the modern game that will give you one game out of 10, it's as simple as that.
"Coupled with fact that he gets so much reputation and baggage and everything that comes with it, I don't think Mikel Arteta wants that anywhere near that Arsenal.
"He has to get away from Manchester United. I think it'll be an MLS (move) or something. It's going to have to be a massive wage cut."
Foster also said: "Once that fire goes, can you get that back? It has to come from him. I don't think he can get it back.
"Again, you're talking about money which does really ruin everything lads. Once people have that massive contract and they've got that five years in the bank and they've got everything they'll ever need for the rest of their life, that takes it (that fire) away.
"They were talking £40m you know as well. Even 10, I ain't paying £10m... because of everything."