Forget his horrendous disciplinary record or nauseating Twitter presence, QPR's biggest Barton bug-bear should be his lack of on-pitch contribution.
Another week, another card for Joey Barton.
After seven yellow cards on the trot, the notorious hothead ended that streak in fine fashion - sent off in the defeat to relegation rivals Hull City for a mindless thwack to Tom Huddlestone's nether region.
It wasn't his worst outburst of violence - not even in his top three - but it once again exposed the former Newcastle United midfielder as a liability.
That Rangers have handed him the captain's armband is laughable.
But, Barton sympathisers quite reasonably point out - yes, there are some out there - that collecting cards is just a part of his game, peddling that stale cliché about ruining a player if you take away his fire.
Maybe. However, the thing is, Barton hasn't been much of a player this season.
Letting down team-mates and supporters through an inability to control himself aside, and the controversial figure hasn't brought much to the table that QPR are sliding down rapidly.
While he may be a combative character, there's supposed to be more to his game than a tough-tackling hardman. This is a guy who often takes set pieces at Loftus Road, and is capable of producing a pass.
Just not this campaign, it would seem.
In 19 Premier League games this term, he has produced a solitary assist, and created just seven 'big chances', according to Opta.
That's an average of creating a chance once in almost three games. Matt Phillips, who has played less than half the minutes Barton has, has three assists. Clearly, Barton isn't bringing incision to the party.
Nor is he providing a reliable unit when in possession - losing the ball 342 times in the league this season, the most of any of the QPR outfield players.
He has a passing accuracy of 73%, with team-mate Leroy Fer more reliable, completing 80% of his passes.
In the final third, Barton's ability on the ball is even more erratic - with 43 per cent of his attempted passes going astray. Rangers would be better off relying on Fer, who has completed 67% of his final third passes this season, or Mauricio Isla (69%).
And the final proof of a miserable season for Barton is his miserly crossing accuracy, with two thirds wayward.
My colleague Tim Poole wrote earlier today of club doubts over renewing Barton's £75,000-a-week deal in the summer.
From where I'm sitting, QPR should be filled with certainty - his time at Loftus Road is up.