Manchester United forward Wayne Rooney has defended Chelsea striker Diego Costa in the wake of recent criticism and feels the Spain international played a key role in his side's victorious Premier League campaign in 2014-15.

Costa netted 20 goals in 26 league appearances last term to lead Chelsea the way, but he has been less influential this campaign.

The striker has scored just twice in 10 Premier League outings so far, but Rooney has hailed his fighting spirit and believes he remains a key figure for Chelsea.

"I think what Chelsea missed the season before was that fight up front and he gave them that. I strongly believe that's why they became champions," Rooney was quoted as saying by Daily Star. 

"I actually voted for Costa as player of the year last season because I think he was a huge player for Chelsea. 

"Obviously it hasn't gone as well as it did last season for him, but I think he is a fantastic player.

"He's a fighter and I think that's part of his game and it's going to be very difficult for anyone to ask him not to do that. I feel that's in him - that fight. He thrives on that and that gets his team-mates going as well."

Costa is expected to lead the line for Spain when they take on England on Friday.