The Indianapolis Colts plan to allow Peyton Manning to become a free agent, sources told ESPN on Tuesday. The formal announcement will reportedly come at a press conference Wednesday. The four-time league MVP intends to continue to play, the source said, but the Colts have decided not to take on the $28 million bonus and four years remaining on his contract (NFL contracts are not guaranteed). Manning missed the 2011 season after an injury that required surgery on neck vertebrae, but reports are that his physical condition has considerably improved in recent months. Early rumors put the Arizona Cardinals as the frontrunner as to who might acquire Manning. The Miami Dolphins are also said to be in the running.