On international duty, club rivals become team-mates for a week or two.
Santi Cazorla has been speaking about playing with Diego Costa and is backing the striker to improve on his current record for his country.
After opting to play for Spain rather than Brazil, the country of his birth, the striker has disappointed and scored just once in seven international performances. That goal came in a 4-0 defeat of minnows Luxembourg.
“I speak to Diego a lot and he says he’s feeling great,” Cazorla said before Saturday’s game against Slovakia. “On other occasions when he’s come to the Spain squad with injuries he has not been in his best physical condition.
“Right now he feels good and he’s enthusiastic. He’s going to be a vital player and hopefully he can score lots of goals.”
Saturday’s game against Slovakia is a big one. Spain lost to Slovakia, who have won all six of their qualification games so far, last year and trail the underdogs in their qualification group. Vincente del Bosque’s men have to reply and they’ll need Costa to take any chances that fall his way.
The striker has just one goal in four Chelsea appearances so far this season, but Cazorla still has faith in him to turn his form around.