Yes, it means his career is more than half over.
If you think that's a negative comment, then I suggest you pop another one of the blue pills.
Broken heart?
Here is some casual "expression counselling" for your benefit Mr Willow:-
"Backend" does mean more than half-way through. Its a term more closely aligned to a circumstance of being in a "final stage"
And if a player is reaching his final stage as a footballer, then he obviously is facing some kind of impediment, be it age or other disability or indeed, demand.
In other words, it is reasonable to imply a negative connotation.
Now I dont think Coops is in this category.
And theres also no need for you to get abusive over what amounted to a "nip on the toe" correction.
A more appropriate means of reply would have been to make clear what you meant and apologise to Coops if anybody misinterpreted you.