• Chelsea striker Diego Costa.

Chelsea striker Diego Costa. (Photo : Getty Images)

English Premier League side Chelsea FC is reportedly furious about the alleged luring tactics being done by La Liga outfit Atletico Madrid in trying to reclaim their former striker Diego Costa this summer.

Chelsea even threatened to report the Spanish capital city squad to the sports' world governing body, FIFA, if they continue on with trying to release rumors that the 27-year-old Brazil-born Spaniard is unhappy at the Stamford Bridge and is already on his way back to the Vicente Calderón Stadium.

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The Sun reported that the Blues "have written a second complaint to the Spaniards, expressing fury at noises allegedly coming out of Madrid suggesting Costa is 'close' to re-signing for Diego Simeone's side".

Meanwhile, Atleti president Enrique Cerezo had refuted such accusations, saying that the quotes ascribed to him by the local Spanish media were really not his.

According to the report, one Stamford Bridge source disclosed that Chelsea is going to write to Atleti again, "but if this continues there are further options open to us, which includes reporting them to FIFA. We sincerely hope it does not go that far".

New Blues boss Antonio Conte had spoken forcefully about such matters, saying that "it is normal to ask for respect".

The 46-year-old Italian mentor admitted that he does not fully know about the allegations to Atleti, but he knows his "attitude and behavior" will not allow him "to speak about the players of other clubs".

"I'd like that others don't speak of the players of my team. I know this period is strange. We respect all - but we want respect," said Conte. "Diego has not put in a transfer request and is our player."

"He has shown that he is the strongest striker in the world. I'm sure that also when he gets into this idea of football he can score a lot of goals for us," he added.

However, Conte is also realistic, leaving an open door to the speculations by saying that he is not 100 percent sure that Costa will stay with his squad next season.

Caught Offside indicated that the Blues allowing the 6-foot-2 striker to leave this summer is really unlikely, which could be "interesting to see whether the rumors persist now that Atletico have been threatened with legal action".