As the Guardian points, Joey Barton's hysterics gave City the extra time they desperately needed to transform their fortunes. Conversely, Barton going neanderthal also sank United's Premiership hopes. If I were him, he would be well advised to steer clear of anything movable that Sir Alex could get his hands on.
And a corollary to this all. Could there be any more significant elbow in the history of the Premiership as the one Carlos Tevez landed on Barton? The Argentinian did not contribute anything with his feet but his elbow, now that is immeasurable.