Manchester United manager Sir Alex Ferguson has made the worrying admission that there has been "no improvement" on a calf injury picked up by Rio Ferdinand. England centre-back Ferdinand will not play when the champions make the trip to west London on Sunday to take on Premier League leaders Chelsea. He is also not expected to be involved in England's friendly against five-time World Cup winners Brazil in Qatar next week. Old Trafford boss Ferguson revealed the situation had not got any better than when Ferdinand first picked up the injury a couple of weeks ago and that it could be related to a lower back complaint. "There has been no improvement," said Ferguson. "We are having to look at something different because usually you are back from a calf injury within two or three weeks. "But there is no sign of recovery from this injury so we are looking at whether it is to do with his lower back."