Spanish newspaper Mundo Deportivo claim that Chelsea have agreed a clause in the contract of Diego Costa which would allow him to return to Atletico Madrid in the winter transfer window. The clause is for €40m/£28m and Mundo Deportivo say Atletico are evaluating whether to trigger it. A €40m clause would sound very unlikely to us. Costa isn't having a good season but he certainly did last year and it would appear odd for Chelsea to allow such a contract stipulation. it's not a common thing for British clubs to include and the amount isn't high enough to have scared off other interest if Costa had done brilliantly well for Chelsea. Just imagine if Costa had scored 30 goals last season and was on the way to more this season, only for Atletico to take him back for €40m, it doesn't add up. Nevertheless, Mundo Deportivo say that's what the situation is. Costa's strop at the weekend after warming up and face like a smacked behind won't have gone down well with Jose Mourinho, regardless of what he says publicly. Costa's on pitch antics are worth putting up with when he's scoring goals but if his attitude is questionable off the pitch, and he isn't scoring goals, it's not a great situation for Chelsea. http://sportwitness.ning.com/forum/topics/chelsea-agreed-28m-fee-for-january-transfer-evaluation-on-trigger