Chelsea announced on Sunday that they have reached an agreement to sign Brazilian attacking midfielder Willian from Russian side Anzhi Makhachkala, subject to the granting of a work permit.
The 25-year-old had been set to join Tottenham Hotspur, having undergone a medical at the north London club earlier this week, only for Chelsea to hijack the deal.
British media reports claim Chelsea will pay a fee of around STG30 million ($A52.22 million) to secure Willian's services.
"Chelsea Football Club can confirm an agreement has been reached with both Willian and his club Anzhi Makhachkala for the transfer of the Brazilian player," read a statement on the Chelsea website, www.chelseafc.com.
"The transfer is subject to a work permit hearing on Wednesday."
Willian will be the fourth player to join Chelsea during the current transfer window, following Socceroos goalkeeper Mark Schwarzer, Dutch midfielder Marco van Ginkel and Germany international Andre Schuerrle.
His arrival will further swell the number of attacking midfielders at manager Jose Mourinho's disposal, with Eden Hazard, Juan Mata, Oscar, Victor Moses, Kevin De Bruyne and Schuerrle already competing for just three starting places.
Willian only joined Anzhi from Ukrainian side Shakhtar Donetsk in January, but he is being moved on after the Russian side's billionaire owner Suleiman Kerimov decided to restructure the club and drastically shrink their budget.
Speaking before the announcement that an agreement for the transfer had been reached, Mourinho said he felt no sympathy for Spurs despite swiping the player from beneath their noses.
"That's the danger of medicals before contracts. But you have to do the medical before," he said.
"The best thing to do is the medical in secret. If the player is fine, you can sign him. If he's not, you don't have to destroy his career. Sometimes there are sources who find out everything."