Diego Costa Suspension Is Unwanted Additional Concern for Jose Mourinho

First it was injuries, now it's suspensions keeping Diego Costa out of the Chelsea team.

Following his indiscretions against Sunderland this weekend, Jose Mourinho must be more frustrated than ever with how Costa's season is developing.

Of Chelsea's 20 games this term, Costa has already missed five through injury. Being suspended for the visit of Tottenham Hotspur to Stamford Bridge on Wednesday will make it six, which is over a quarter.

That trend can't continue if Costa's going to be the man to deliver trophies to Stamford Bridge—which is the very reason the club splashed out £32 million on him in the first place.

Costa's suspension was avoidable, but he allowed himself to be dragged into a physical battle—one born out of frustration with how Saturday's game developed and his treatment by the Sunderland defenders.

The Spanish international lost his cool at the Stadium of Light, leading him to pick up a cheap booking—his fifth of the season.

There is a debate as to whether or not Costa would have started Wednesday's London derby given the fixture congestion Chelsea face this coming month, although Mourinho's decision has now been made for him.

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Since the start of the campaign, the Chelsea manager has worked hard to protect Costa's fitness. He's been rested at times, and after missing much of October with his on-going hamstring troubles, a very public spat with Spain coach Vicente del Bosque saw the striker omitted from November's squad.

By hook or by crook, Del Bosque made the right decision. It was one that benefited club, player and country in the long term, only now Costa's decision-making is benefiting nobody other than the opposition.

Costa has been unfortunate with some of the decisions that have gone against him this season—think the booking for simulation against Burnley in Chelsea's opening game of the season, which should instead have been a penalty.

"We have explained to him what we expect in the Premier League, what people like and what people don't like," Mourinho said after that Burnley victory when asked by a journalist if he was worried about the nature of the yellow card.

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"The kid presents himself with a fantastic attitude, a competitive attitude, but clean and polite. He has a clear penalty and no penalty, but a yellow card. The kid was obviously frustrated, so I hope he doesn't get more unfair decisions."

Costa has no such excuses this time.

Whether right or wrong, his reputation for being aggressive and having a loose switch has followed him from La Liga to England.

He was always going to be targeted to get a reaction, and regardless of whether or not referees have been quick to act with that reputation in mind, Costa should have shown more control.

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Against Sunderland, it was actually the opposite of what we have seen previously. If anything, Costa was treated favourably by referee Kevin Friend after first kicking out at John O'Shea before striking Wes Brown in the face with a flailing arm in an aerial collision.

Regardless of what led to those incidents, Costa shouldn't be risking a red card—or a yellow for that matter—by reacting the way he did.

With a title and games to be won, Chelsea and Mourinho don't need the attention that follows on the back of the goalless draw with Sunderland.

What they need instead is their striker on the pitch, adding to the 11 goals he has already scored this season.

Alastair Grant/Associated Press

Costa has already proved himself a shrewd purchase by Chelsea. He is the biggest threat this team has had in front of goal since Didier Drogba's heyday and is exciting to watch.

He's reinstalled the fear factor, but defences aren't going to be concerned by him watching games from the terraces.

Injuries happen, yet suspensions are avoidable. More so than ever, Costa is going to be a marked man in the Premier League and Mourinho is going to have to deal with it.

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