Petrov certainly didnt become captain as soon as he joined.
I would like all the team to be leaders, as in the golden era. Sir Dennis was the captain, but was not massively demonstrative. We had leaders like the two centre backs, Peter Withe especially, Des Bremner, Kenny Swain, Jimmy Rimmer and even Gordon Cowans took control. I wouldnt mind Bent as captain and lead by example so long as he had others helping him out. Know a forward generally is frowned on, but he seems to have the respect of the players and is a team player