Chelsea face serious competition from Manchester United if they want to sign one central defender this summer. Chelsea are likely to be in the market for a centre-back when the transfer window opens. They look set to lose one of their current options and a very experienced one, Thiago Silva. The Brazilian’s contract expires at the end of the season. Mauricio Pochettino has also had to deal with a lot of injuries in central defence. Wesley Fofana, for example, is still out injured. It has been reported that the Blues and several other English clubs, including United, have been offered the chanc…