He adds that there is no internal debate regarding that decision.
Raanan believes the Giants would have to be out of playoff contention for rookie quarterback Daniel Jones to get a crack at starting this season.
The Giants have had trouble in the past benching Manning and allowing younger quarterbacks to play.
As recent draft picks Kyle Lauletta and Davis Webb failed to start a game in either of their seasons with the Giants.
Jones impressed this preseason, completing 29 of his 34 attempts and posting a passer rating of 137.3.