#5. Tommaso Ciampa

Tommaso Ciampa was in the midst of what may have been the greatest NXT Championship reign of all time. It was first rumoured in February that Ciampa had been dealing with a major neck injury.
The worst was confirmed when WWE confirmed Ciampa's injury status. Around March, he underwent anterior cervical fusion surgery, one that's done to remove any pressure from the spinal cord. They also replaced the ruptured disc with a donor bone and also some bone from his hip.
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In a Tweet following the surgery, Ciampa revealed that the doctor told him he was on "borrowed time" - quite a scary prospect, especially given that he was coming off the greatest run of his career.
Triple H revealed on a conference call after NXT Takeover: XXV that Ciampa had been cleared for non-physical activity, but is still far from recovery. He did admit, however, that Ciampa is ahead of schedule in terms of recovery.
Cleared for non-contact means you can’t do anything in this business. He’s ahead of schedule and doing extremely well. Ahead of schedule on all of it and moving along. But with the type of injury he had and the type of surgery he had, especially in this from a physicality standpoint, you’re not doing anything until you’re 100 per cent.