But the Villa boss insists the capture of 34-year-old Marshall should not discourage academy graduate Elliott Parish from trying to stake a first-team claim.
"We'd got the two goalkeepers and young Parish and if we were fortunate enough to get through against Rapid Vienna in the Europa League, which is far from certain, then we would need to have some extra cover," he said.
"I know Marshall from my Norwich days. He was only a kid and he didn't play too often because Bryan Gunn was in goal but I think he'll be capable of giving us that little bit of experience and allowing the likes of Parish and the younger boys that we have a bit of faith in to be able to develop in their own time.
"Marshall has said: 'If I'm doing really well and I get the opportunity, would you take the chance of me going in?'
''And the answer would be absolutely, if he's performing excellently."