Costa Tensions Rising  (Sky Sports)

Jose Mourinho's strained relations with Diego Costa could hamper Chelsea’s recovery, writes Adam Bate.

Afterwards, Mourinho stood firm. The Chelsea manager had seen his team play out a goalless draw away to an in-form Tottenham side that has been unbeaten in the Premier League since the opening day of the season. He was emboldened by an organised performance.

Asked about Costa, the striker he had dropped for this game, Mourinho said: "I think Diego is very privileged because he was the last one to be on the bench. Everyone else has been on the bench. The captain was on the bench. [Branislav] Ivanovic was on the bench.

"[Gary] Cahill - the vice-captain of England - was on the bench. [Cesc] Fabregas was on the bench. Pedro was on the bench. [Eden] Hazard - player of the season - was on the bench. Oscar was on the bench. Everybody. So Diego is privileged I kept him in the team for all these matches."

He didn't look like a man who was feeling particularly privileged on Sunday. Indeed, Costa's frustration was hard to miss. He'd spent much of his afternoon as a brooding presence on the sidelines but did warm-up when requested in the second half, perhaps reflecting on his falling stock.

He'd scored the opening goal in this fixture last season. In the previous meeting between the sides, he had picked up a Capital One Cup winners' medal at Wembley. But here he saw Kenedy and Ruben Loftus-Cheek get the nod ahead of him, while Hazard played out of position up front.

In truth, Hazard impressed. He offered good mobility - his 71 sprints were more than anyone else on the pitch - and was heavily involved, having more touches than any other Chelsea player. But a header went over the bar and the only shot on target was well saved by Hugo Lloris.

It's difficult to imagine even Mourinho believes this is a long-term solution. For now, the priority is finding something for his struggling side to build on. As a result, he spoke of getting his team back, seeing a better spirit and being very happy with his decision to play Hazard up front.

That there's little reason to doubt he meant it says much for Costa's declining influence. And yet, the striker's annoyance was apparent nevertheless. He exhibited it by flinging his bib in Mourinho's general direction upon the realisation that his services would not be called upon.

It's been that kind of week. There were words exchanged between Costa and Mourinho during the team's Champions League win in Israel in midweek, while the manager had indulged himself in much head-shaking prior to the player's winner against Norwich last weekend.

Although the Spain international has been a popular figure among supporters, their sympathies are likely to remain with the coach. Certainly, it's easy to understand why Mourinho's faith has faded. Willian, for example, has scored more from free-kicks this season than Costa has managed in total.

Even own goals have boosted the Chelsea cause as much as Costa. He has as many Premier League bookings as goals and his four strikes this season have come against Aston Villa, West Brom, Maccabi Tel Aviv and Norwich. The competition has been stiff at Stamford Bridge but his slump might just be the most marked of all.

Diego Costa scoring record

Season	Club	Competition	Appearances	Goals
2013/14	Atletico Madrid	La Liga	35	27
2014/15	Chelsea	Premier League	26	20
2015/16	Chelsea	Premier League	11	3

That's particularly extraordinary given how much was made of the idea that Costa was precisely the player that Mourinho's Chelsea had been waiting for. Now it's Costa forever waiting, lingering on the back-foot and hoping for chances to be laid on rather than making things happen for the team.

He is not without excuses in this regard. Even at his Chelsea best, Costa relied on quality service. According to Opta, 16 of his 20 Premier League goals last season came from what could be defined as clear-cut chances. His great strength was the efficiency with which these were dispatched.

Premier League 2015/16 - Striker comparison

Player	Club	Clear Chances	Converted
James Vardy	Leicester	14	8
Olivier Giroud	Arsenal	14	5
Harry Kane	Tottenham	12	7
Romelu Lukaku	Everton	12	6
Sergio Aguero	Man City	10	3
Diego Costa	Chelsea	4	3

The Premier League goal tally is down from 11 at this stage last season to just three. But it's not the finishing that's the problem. Indeed, the stats suggest he has scored from three of his four clear-cut openings so far this season. That's a better conversion rate than Jamie Vardy and Sergio Aguero among others.

The issue appears to be that he's not getting into the positions to score. Costa could point to the delivery from Hazard and Fabregas but he has seemed off the pace too often for Mourinho's liking and the player himself has acknowledged that his fitness levels have not been good enough.

Maybe I got out of my diet and, when I came back, I was not the way I was supposed to be. I was a little bit overweight. That affected my game.

As a result, it's not only the lack of goals that have harmed Chelsea. Costa's contribution was far greater than that as he harried opposition defences, ran the channels and gave his team a foothold in the final third. The failure to make his presence felt has been a huge backward step for his side.

Without Costa, Mourinho finds himself facing similar problems to those that he encountered prior to the player's arrival from Atletico Madrid. The coach frequently bemoaned the lack of a top-class striker despite the presence of Samuel Eto'o, Demba Ba and Fernando Torres at the club.

Mourinho appeared to regard a third-place finish as the natural ceiling to that squad's ambitions in 2013/14, an acknowledgement that the job could not be done without the right forward. Of course, he'd welcome third spot right now but the form of a third-place team won't be enough at this point.

For all Hazard's enduring quality and improved enthusiasm, Chelsea need Costa back. They need the player who scored 57 club goals in the previous two seasons. Bit-by-bit, Mourinho is building Chelsea's confidence back up. But the limitations are obvious if he cannot build bridges with Costa too.