In the NFL, star players are considered irreplaceable until proved otherwise. Take Tom Brady: The 2007 NFL MVP would've topped any list of the most irreplaceable players in football this time last year, but by the end of the season, Matt Cassel was considered to be an adequate impersonation of the guy who had put up the best season of any quarterback in NFL history.
5hAdam Schefter and Chris Mortensen
7hPablo S. Torre
4hDavid Purdum and Ryan Rodenberg