As Eagles doctors were giving newly acquired running back Jerome Harrison his physical, they discovered a brain tumor that nullified a trade with the Lions, according to two league sources. The trade might have actually saved Harrison's life, the sources said. Without the deal being made, Harrison would not have undergone a physical. The tumor is now being treated, according to sources. Harrison could not be reached for comment. The Eagles would have sent Ronnie Brown to the Lions in exchange for Harrison and an undisclosed pick in the 2013 NFL draft. Harrison is not expected to play again this season, but his long-term prognosis both for life and his football career appear to be good, sources said.