Chelsea's inside man on securing £50 million duo revealed

Diego Costa attempting an overhead volley

Chelsea are poised to sign Diego Costa and Filipe Luis, and it is former player Tiago who is said to be the crucial player who helped ready the deal.

Diego Costa's impending transfer to Chelsea is the worst kept secret in football, with the striker even commenting over the weekend that 'it looks like' the deal is happening.

He is not the only one, reports widely claim that full-back Filipe Luis is bound for Stamford Bridge, with £50 million for the pair expected to activate their release clauses and send the pair to London.

Of course simply fronting up the money is not the be all and end all, Costa and Luis actually had to be persuaded to leave the La Liga champions for the Premier League's third placed side last season.

A third player, Tiago Mendes, who played for Chelsea during 2005/06 and is reported to be re-signing on a free transfer, is being credited as the key man behind the Blues being so close to wrapping up the deals, described as 'decisive' in the moves by the Spanish press.

Spanish newspaper El Confidencial report that Jose Mourinho, who has retained contact with Tiago and already convinced him to sign on a free, has been Chelsea's inside man helping persuade Costa and Luis to follow him.

"Most important has been the power of seduction that he (Tiago) has had on Filipe Luis and especially with Diego Costa. And the former Juventus man has been key to the smooth operation of the deal and especially crucially support off the field."

The paper report that Mourinho had dispatched Tiago to help convince Costa, and once he persuaded the Spanish international, moved onto Luis - all while orchestrated by agent Jorge Mendes.

When the deal is finally announced, Chelsea will be instantly improved by a trio of players from last year's Champions League runners-up, who knocked them out in the semi-finals.

While David Moyes struggled to attract players to Manchester United through his own inexperience, Mourinho appears to live by the virtue that it is who you know as well as what you know which helps bring about success on the transfer front.

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