great GK always come more from experience than talent.
back to back games and playing important match with lots of crowd really help making a great goalkeeper. shoot,try from opposition also help a lot making a GK to be better.
theres only few great world class GK like buffon,casillas,cech..
but there still many really good and experience GK out there. in EPL itself i really think GK like given(ex-newcastle), green(eng no.1?),howard(been better with more match), friedel(very experience), reina(fast reflexes), cudicini(better than gomes), schwarzer(really good last season).
can see the talent in foster but he really need lots of match to be a good GK. hope he still get some match mostly in league cup,fa cup and some epl,CL when VDS came from injury. or maybe united should get someone more experience to backup VDS on january and loan foster somewhere where he can get more matches and make more saves