Obviously, any position could lose the atarter due to injury, most it would be hard to fill with a reasonable replacement (that could learn and do a decent job).
Brady, Wilfork, Gronk, Chandler Jones would be pretty hard in the short or long run.
Slot receiver? Edelman, Collie, Moe, Boyce and that's without looking outside the organization.
Emanuel sanders, if we go after him, Davone Bess if we could get him for nothing and fix his brain. Lots of possibilities that might be available for nothing or very low picks, as all ours for years have been.
It's not that big a deal. DB Wheatley had some condition with his wrists that made him "injury probe" but most players get a number of unrelated injuries during their careers, sometimes in bunches. This is the situation for Gronk (except his back) and Amendola (broken collarbone, dislocated elbow and groin tear couldn't be a more random set of injuries.
No one knows who will get injured. Last year, the injury prone one was Edelman, and that's an "injury prone" one (foot bones can be chronic problems.
Summarize: No crystal ball (we will have injuries) slot is an easier position to replace cheaply than most (many small quick receivers, often low picks or UDFA).