Coton believes United should stick with David de Gea because he does not see any worthwhile alternatives that could realistically be attracted to the club.
"Over the years we looked at a lot," he said. "We looked at Buffon but there was no way we could get him. He just didn't want to come out of Italy.
"We tried to get Edwin van der Sar a lot earlier than we did but it didn't happen.
"It is not a matter of 'it is Manchester United, we must be able to get them'. There are certain situations when you can't."