If you were a punter in the pub or on a forum you'd say he's like a pub player when he has a bad game and everyone would know what you meant. If you're meant to be an expert worth listening to, you'd say something at least on nodding terms with reality and hopefully insightful. When McGinn, or anyone, has a bad game, they have a bad game at the highest level against the 0.0001% who can even get close to that level.
Roy Keane is and always has been a twat. He always will be a twat. He was a genuinely brilliant footballer who, like McGinn, was pretty much unmatched in his role but, unlike McGinn, entirely sullied any legendary status he might justify by being a dirty, arrogant, thick, solipsitic cnut.
He remains the lobotomised, one-eyed man's Des Bremner. That good but, somehow, not fit to breathe the same air as either Hibbee giant.