Tim Tebow -- STALLONE HAS MY BACK ... 'He Should Be 1st String!' (Video)

Tim Tebow has some MAJOR support from a big huge Philadelphia mega-icon -- Sylvester Stallone -- who tells TMZ Sports Tim shouldn't just make the Eagles roster ... HE SHOULD START!!!!

Stallone was out at Cafe Roma when he told us why he hopes Chip Kelly and the rest of the Bird Gang make the RIGHT move and sign the former Heisman Trophy winner to the squad.

"How can you not like Tim Tebow?"

Looks like Stallone could get his wish -- with the Eagles trading away Matt Barkley after Tim balled out on Thursday night ... it looks like Tebow has a realistic shot of making the team.