His spokesman said: "Tobey has experienced mild discomfort in his back, which is in the final stages of healing. Everyone involved wants to be certain he is able to do the intense stunts."
But nothing's definite yet - and Spidey fans everywhere hope he'll be well enough to play Peter Parker again.
But there are reports that upcoming heart-throb, Jake Gyllenhaal, has been lined up to replace Tobey if he can't do the role.
Jake's starred in films like The Good Girl with Jennifer Aniston.
If he does take over the role, it'll be interesting for Spider-Man actress Kirsten Dunst - as Jake's her real-life boyfriend!
But if she knows anything, she's not giving it away. In a recent interview she said: "I really, honestly, don't know what's going to happen and whoever is in the movie, I start April 12, so that's all I know."