Former Chelsea manager Gianluca Vialli has stated his belief that Diego Costa remains one of the best strikers in Europe.

Costa has endured a drastic dip in form this season and his poor performances, as well as unnecessary antics, have led to the Spaniard being vehemently criticised from all corners.

However, Costa did manage to show glimpses of his old self during Chelsea's 2-0 Champions League victory over Porto in midweek and following the game, Blues legend Vialli has stated that the 27-year old still has plenty of quality.

Vialli said: "I think he's one of the top 10 strikers in Europe.

"He proved it last year and seasons before in spain. He's obviously going through a tough time, but it's not entirely down to him.

"Sometimes it depends on the quality of service from offensive midfielders. If I was Diego Costa I would train hard but play easy, which means you try hard without trying too hard."