Chelsea manager Jose Mourinho has praised Diego Costa for his impressive start to life at the club.

The striker bagged a hat-trick as the Blues claimed a 4-2 win against Swansea City this afternoon to maintain their lead at the top of the Premier League.

Costa has now scored seven goals in his first four games for the club and Mourinho admits that he has been surprised by his form.

"If the team plays well he has to score goals. Seven goals in four Premier League matches are maybe too much – we cannot expect him to have 14 goals after eight matches. It surprises me because it's not normal – you cannot repeat it in a cyclical way," Chelsea's official website quotes Mourinho as saying.

"He's comfortable in the team. I think now everybody knows Chelsea did the right thing in waiting for him and not going to the market in the last summer of 2013 or in January this year, just to buy a striker.

"If he keeps scoring a few goals, a few goals gives points and points help the team to be in the top part of the table."

Costa joined Chelsea from Atletico Madrid in July, for a reported fee of £32m.