In Spain they call him “Que Crack”. It’s a curious, ungrammatical street phrase that can be translated as “What’s happening?”, or “Isn’t that something?” or, in a footballing sense, “That’s one fantastic player”.

Atletico Madrid fans apply it to Diego Costa, while Chelsea fans, who know a star when they see one, are still struggling to come up with a tag to properly describe the goal-hungry talent they already idolise.

He’s head and shoulders ahead of the pack in the Premier League list of top scorers, but the sharp wits in the Matthew Harding lower, who often originate the best chants, have yet to devise a song for Diego that feels right.

Meanwhile, Fernando Torres, and his £50m millstone, now seems like a distant memory.

Costa looks older than he is. In fact he celebrates his 26th birthday two days after this weekend’s crunch game against Arsenal at Stamford Bridge.

The man is an international conundrum. He was born in Brazil, but began his football career in Portugal before moving to Atletico.

He played friendlies for Brazil before deciding he was Spanish, but Spain coach Vicente del Bosque keeps being told the free-scoring, rock-solid striker is injured, and can’t play for his country.

Observers feel Jose Mourinho has called everyone’s bluff for too long, and will have to release his number 19 to play in the matches against Slovakia and Luxembourg during next week’s international break.

Costa, supposedly suffering from hamstring trouble, played the entire match against Sporting Lisbon in midweek, even if it was Nemanja Matic who headed the goal that gave the Blues three Champions League points in the Portuguese capital.

And so to Chelsea v Arsenal on Sunday.

If the Blues can make a few more chances count, then victory is within their grasp.

They had opportunities to make the Lisbon result more emphatic, but decided to hold back until the Gunners’ visit.