Diego Costa
Diego Costa has scored seven goals in four gamesGetty

Chelsea manager Jose Mourinho has labeled Blues striker Diego Costa 'not normal' following his hat-trick against Swansea City on Saturday.

The Blues signed Costa from Atletico Madrid in the summer and the striker has lit the Premier League on fire and given Mourinho's men the perfect start to the campaign.

The Spanish international, has been on top form from the very first game and has already scored seven goals in four matches in the league. The Portuguese boss believes that as long as the team plays well, Costa will keep scoring goals but believes is wrong have a the same expectation every time.

"If the team plays well, he has to score goals. Seven goals in four Premier League matches is maybe a bit too much – we cannot expect him to have, say, 14 after eight games – but the way he's playing… If he keeps scoring as he is, that will give us a chance to stay at the top," Mourinho said, as quoted by the Guardian.

"He hasn't surprised me. Maybe seven in four has surprised me – that's not normal – but he's comfortable in the team," the Blues boss added.

The former Real Madrid manager also admits that Chelsea were looking for a particular type of striker to suit their system, and that's why the west London club did not buy any striker mid-season during the 2013/14 campaign, despite their struggles to find the net.

"We were building the side in a way where we were waiting for a certain type of striker. I think everyone knows now why Chelsea did well to wait for Diego rather than buying someone else in the midwinter last season."

Chelsea have also re-signed former striker and club legend Didier Drogba, and Mourinho believes Costa can have the similar impact for the club.

"We didn't want just to buy a striker. It is hard to compare with Didier. He started in 2004, 10 years ago, and had a fantastic career here. But Diego has shown he can have that same profile of career, yes," Mourinho remarked.