As a lawyer, I would say "cheat" as applied to a footballer is in a different category to accusing someone of being a rapist.
The test as to whether or not a statement is libellous is that it tends to lower someone in the estimation of right thinking people generally. Even if that test is satisfied, a libel claim can be defeated if the statement can be proven to be true or if it is (even if it cannot be proven to be true) fair comment on a matter of public interest.
Dazzler....There is no need to start all you contributions as a lawyer, this site is only used by lawyers even if they are of the barrack room variety
If you call someone a rapist you are saying (obviously) they have raped someone. That would (equally obviously) tend to lower them in the estimation of right thinking people generally and would be libellous unless you could show it to be true. Calling someone as a rapist cannot be fair comment as it is not a comment. It is a statement of fact which is either true or untrue.
Calling Quinn a "cheat" is not the same. In context, I take it to mean that Quinn is not putting in sufficent effort on the field to warrant his pay. This could tend to lower the estimation of Quinn in the view of right thinking people generally, but I think if he brought a libel claim on that basis, a defence of fair comment would defeat it. The allegation of "cheat" is a comment on Quinn's performance and I don't think it is too extreme to go beyond the bounds of fairness.