The Spain international could yet have his current ban extended by the governing body, and the Blues boss Guus Hiddink is not happy with the authorities
Costa will sit out Saturday's London derby against Premier League high-flyers West Ham at Stamford Bridge after he was sent off for an altercation with Gareth Barry during last weekend's FA Cup sixth-round defeat at Everton.
Television replays of the incident that resulted in the striker's second yellow card suggested he might have bitten Barry, although both players later denied that was the case.
Costa was cleared of any wrongdoing by the FA over a gesture he aimed towards the Everton fans at half-time, but he could still be hit with an extension to his ban through a charge of improper conduct that relates to his behaviour directly after receiving a red card for the Barry clash.
And Hiddink is uneasy over the rap sheet with which his forward, who was left out of Spain's international squad on Friday, is being confronted.
"First, everyone wants to get on his kiss or 'bite', and Barry made a very good statement by saying what has not happened in this case," said the veteran Dutchman.
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"Maybe there was a little bit of searching for where we can get Diego, and there he was frustrated.
"If you cannot prove the bite sometimes, in my opinion, they are looking a bit for where they can chase him. The officials [the FA administration].
"He is a bit marked in this. I know it’s difficult. If the player is frequently bit by bit provoked, you [opponents] play a bit with that.
"It's part of the game, how far can you get someone out of his comfort zone and into the red zone?
"I have said I cannot guarantee Diego will not explode but I sometimes get the impression they [the authorities] go for him.
"What I smell and didn't like, and what I spoke about with Diego this week, is we both had the feeling they could not charge him on the kiss, but 'let's see what else we can get him for.'"