Chelsea manager Roberto di Matteo has said that the recent controversy surrounding referee Mark Clattenburg was not the reason that they drew against Swansea City yesterday.

A police investigation into what Clattenburg allegedly said to Blues midfielders John Obi Mikel and Juan Mata is now underway.

However, the Italian refused to use the incident as an excuse, instead believing that back-to-back games with Manchester United has drained his team's reserves.

"I wouldn't read anything into what has happened and the result," said Di Matteo. "It is very difficult to win away from home in the Premier League.

"We have certainly felt tired this week after the two games with Manchester United, including extra-time."

Chelsea are one point below leaders Manchester United.