His body is completely broken. Pretty sad to see, as he was Fleet footed and a joy to watch in full flow.
The thing is, he wouldn't be the first player in this situation, their body breaking down and not being able to do what they once did.
Many of those players reinvent themselves. They go from that quick, nimble and explosive player and become one that doesn't require natural assets and instead plays smart.
Martial could do that. Become a pure 9, a poacher. There have been players who have suffered horrific injuries that should have ended their career, even meant they shouldn't even be able to walk but yet have come back as a different player. Martials problem isn't as simple as his body letting him down and as much about him not being mentally strong enough to overcome it.
Given United's gaping hole at 9 and Martials inability to be who he was, if there was any determination from him or the club, they could have worked on converting him to a pure 9. It's not as if he doesn't have the tools.
But even as a Martial fan and someone who was hopeful he would get it right, I just don't think he wants it. And at 27, he probably won't ever get it now.