Ill-Disciplined Diego Costa a Warning for Chelsea After Sunderland Draw

Of all the talking points to come out of Chelsea's goalless draw with Sunderland, one will dominate the headlines: Diego Costa's discipline, or lack thereof.

Sunderland defended in numbers on Saturday, providing a resolute defensive unit that Jose Mourinho's side struggled to break down.

They proved worthy of their point, too, working tirelessly to deny Chelsea. In the process, they became the first team to keep a clean sheet this season against the Premier League leaders.

It was the exact same tactic Chelsea have been accused of deploying themselves at times, and with chances coming at a premium, Costa was starved of service. He cut a frustrated figure.

That Sunderland's defenders weren't afraid to play on the edge of the rules in their pursuit of marshaling the Spanish international—adopting some of the darker arts of defending, shall we say—only added to his annoyance, and the inevitable happened.

First, he kicked out against John O'Shea following a heavy tackle late in the first half. Then, he flung an elbow into the face of Wes Brown after the interval. Joe Krishnan felt the referee's call was appropriate:

Costa will count himself fortunate if he is not retrospectively disciplined by the FA for that clash with O'Shea—a factor depending on whether or not referee Kevin Friend includes it in his match report—let alone being lucky to escape with just a yellow card after colliding with Brown.

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The latter incident means he will miss Wednesday's game with Tottenham Hotspur after collecting five bookings this term.

Just as he returns to full fitness, Costa will miss games once more, and it's his own fault.

His temperament has been well-discussed since he joined Chelsea. Costa constantly plays on the edge, and there have been moments when he has run the risk of feeling the referee's wrath.

Until now, it's been very minor incidents here and there—such as at Everton when he confronted Seamus Coleman in a game Chelsea won 6-3.

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At the Stadium of Light, it was different. It was turned up a notch.

Costa was in and out of the game, and it was by far his least productive display in a Chelsea shirt. Sunderland's tactics snuffed his threat, but then he was even more ineffective after losing his head, .

Costa can't control how defenders behave when they play against him. What he does have power over, though, is his own game. Regardless of how often he is kicked, shoved in the back or tackled late, he needs to show restraint.

After soaking up pressure for an hour, Sunderland opened up and got chances of their own against Chelsea. Adam Johnson came close twice, and Connor Wickham forced Thibaut Courtois into a save.

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It was inevitable the home side would have chances of their own, and Chelsea dealt with the threat, containing the Black Cats.

With a man down, that would have been a more difficult task. Had Costa seen red—and he could well have twice—it would have left his team in the mire.

Regardless of the goals he scores, that's unacceptable. Costa can't be playing the hero one week and the villain the next. Title-winning teams don't function that way, and this Chelsea team can't, either.

Mourinho praised Sunderland at the final whistle, but he refused to comment on Costa's ill-discipline.

"I have nothing negative to say about my people," Mourinho told the Sky Sports cameras.

"I didn't see [Costa's elbow on Wes Brown]. But I think the referee was close, and he made, in my opinion, a very good performance. Him and his assistants, I think everything was under control."

Under control Costa wasn't, however, and Mourinho needs to make sure his striker refocuses his attention to the very thing that has made him a sensation this season—scoring goals.

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Sunderland manager Gus Poyet has set out a blueprint for how unfancied teams can get something out of Chelsea. It's not pretty, but it is effective, and for sides hovering around the bottom of the table, these methods can hardly be criticised.

More importantly, keep pushing buttons and defenders know they will get more than they bargained for from Costa.

Garry Hayes is Bleacher Report's lead Chelsea correspondent. All quotes were obtained firsthand unless otherwise noted. Follow him on Twitter @garryhayes