The former Liverpool man was relatively impressive on the wing during his debut campaign at Upton Park, but has flourished at the tip of West Ham's midfield this term.
With one goal from his six league appearances, Downing has also provided some much-needed creativity in a midfield diamond during the absence of captain Kevin Nolan.
Downing has not featured for his national side since Euro 2012 qualifying, but Allardyce feels the 30-year-old is only being denied a place because of the set-up used by Roy Hodgson.
"Stewart's playing in a slightly different role here, I don't think Roy [Hodgson] plays with a man in the hole, or the diamond," Allardyce explained on Friday.
"Stewart certainly has the experience, he's handled the switch of position very well.
"He gets more possession in the position he's in, so that allows him to become more effective. Given his qualities, that's a good thing for us.
"He's certainly not past his best by any stretch of the imagination. You only get past your best when your legs can't take you where you want to go. But Stewart is one of our fittest players.
"He probably should score more goals than he does, but hopefully he'll do that in the new position he's in."
