Rex Ryan was asked about a scenario this morning if Mark Sanchez suffered an injury who would be the to go right in and fill his shoes. Tim Tebow is the answer, but I truly believe it should be Greg McElroy (IF he had the Reps).
If starting QB Mark Sanchez were to suffer a long-term injury, he’d be replaced by Tim Tebow, not Greg McElroy, Rex Ryan said Wednesday.
That may not be a revelation, but there has been some recent speculation — we’re talking out-of-left field speculation — that McElroy would be a better choice because he’s more of a conventional quarterback than Tebow.
Ryan put an end to that.
“We would expand [Tebow's] role,” Ryan said. “We feel good about what Tim could do. We’d be confident in McElroy. [Matt] Simms is the wild card.” per Rich Cimini

Here is my thinking of why McElroy fits:
- He’s a pure pocket passer like Mark Sanchez
- You wouldn’t have to scrap the installed offense or add to it as Rex put’s it if Greg plays
- Tim is affective out of the shot gun, to be fully affective in my opinion, you would need to change the offense for him to succeed.
- You can keep Tim in his role as if Sanchez was playing, keeping him in goal line and wild cat situations.
Of course this only works if Greg gets the work in. As of now, I don’t feel that McElroy has enough reps and Tim would have to be the choice.