Chelsea forced to drop Mata complaint due to lack of proof Chelsea last night admitted that they do not have sufficient evidence to pursue one of their original two claims against referee Mark Clattenburg - but they stand by the allegation that the referee racially abused the midfielder John Obi Mikel during Sunday's Premier League defeat Manchester United. In the hours before they beat United 5-4 at home in the Capital One Cup fourth round, Chelsea announced that the second complaint against Clattenburg, which centred upon what Chelsea players initially thought he had said to Juan Mata, was dropped after an internal investigation. The independent legal counsel, concluded that there was not, in Chelsea's words, "sufficient evidence" to support it. Roberto Di Matteo, the Chelsea manager, said last night that he expected referees to treat his team "fairly" despite their serious allegations against Clattenburg. There is an appetite among the select group officials that Chelsea will have to provide serious evidence that Clattenburg did abuse Mikel or face sanctions themselves. Di Matteo said: "It's incredible to think we have two players sent off in one game again. If I remember rightly one of our sending offs at QPR (last year) was correct and one was probably incorrect. And on Sunday (against United in the league) the first one was harsh but probably correct and the other was 100 per cent not correct. It's incredible it always hits Chelsea football club - maybe that's something we need to think about. We would just like to be treated fairly by everybody. Nobody is talking about the handball in the second half when we should have had a penalty. You have just mentioned two situations (last year against QPR and on Sunday against United) when certainly it wasn't fair, the way we were treated. On Sunday, Chelsea had complained to the match delegate, Nick Cusack, about Clattenburg on two counts. Yesterday's complaint was made directly to the Football Association, which is responsible for disciplinary matters in the English game and have already started an investigation into the incidents of Sunday's match. The investigation has taken in interviews with players and staff which will, Chelsea hope, lend extra credibility to their claims that Clattenburg abused Mikel. Yesterday's statement from the club is the first time they have officially confirmed Mikel as the player at the centre of their allegations against Clattenburg. The club will also deny suggestions that chief executive Ron Gourlay was in Clattenburg's room after the game on Sunday. He is understood to have gone to the area where the officials' rooms are located at the ground when he was told about the dispute and told the Chelsea players and staff there to leave. The statement said: "Chelsea football club [yesterday] lodged a formal complaint with the Football Association regarding inappropriate language directed at John Mikel Obi by referee Mark Clattenburg. This is a result of a thorough investigation carried out by the club, and led by outside legal counsel, of all information available to us including interviews with a number of players and staff. Following Sunday's Premier League game against Manchester United, club board members were quickly made aware, upon entering the home dressing room after the final whistle, that there were allegations of inappropriate language directed at Chelsea FC players by Mr Clattenburg during the game. Board members began establishing the details of the allegations, speaking to all relevant players and staff. After those initial interviews, it was clear that the matter had to be reported. Since reporting the matter to the delegate, the club and outside legal counsel have conducted further investigations. Having completed that process, we have now followed the correct protocol and lodged a formal complaint with the FA regarding John Mikel Obi. There was not sufficient evidence to support a second claim to the FA with regard to the alleged verbal abuse of another first-team player.