Former Chelsea manager Gianluca Vialli believes Diego Costa is still among the 10 best strikers in Europe.
Costa has endured a difficult season, scoring just three Premier League goals as the Blues have slumped to eight defeats in 15 top flight fixtures..
The Spain international was brought back into Jose Mourinho's side for Chelsea's crucial Champions League group game with Porto on Wednesday night, after dropping to the bench for domestic fixtures against both Tottenham and Bournemouth in recent weeks.
But Vialli believes Costa can rediscover his form last season by 'training hard but playing easy'.
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I think he's one of the top 10 strikers in Europe," The former Italy international said.
"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."
