West Ham have snapped up Argentinian Lionel Scaloni on loan from Deportivo La Coruna for the rest of the season.
Scaloni, 27, flew into London on Tuesday evening to undergo a medical and the deal was completed shortly before the midnight deadline.
West Ham manager Alan Pardew was in the market for a new right-back after Tomas Repka returned to the Czech Republic.
West Ham turned their attentions to Scaloni after Barcelona's Spanish international Gabri decided against a move to Upton Park.
Scaloni, nicknamed 'The Bull', is a right-back who can also operate in midfield.
He has won five caps for Argentina and harbours ambitions of winning a place in their World Cup squad.
But Scaloni had become increasingly frustrated at his lack of first-team opportunities at the Riazor and believes West Ham can offer the regular football he needs to press his case ahead of this summer's tournament in Germany.
'The president (Augusto Cesar Lendoiro) was convinced by this particular offer and it satisfies the player on a sporting level as he will have the chance to play,' said Scaloni's father, Angel.
'He was very happy in La Coruna, where the people treated him very well, but the life of a professional footballer has these things and he did not have much chance under Caparros at Deportivo.'
It is not thought West Ham have the option to make the transfer permanent at the end of the season.
Utility man Christian Dailly filled in at right-back on Saturday for the 4-2 FA Cup win over Blackburn, but Repka's departure left West Ham without any recognised right-backs.
Pardew had tried to strike a loan deal with former Hammer Glen Johnson from Chelsea but saw that route blocked by Jose Mourinho.
An arrangement to take Poland international Marcin Baszczyski for the rest of the season with a view to a permanent summer move was rejected by his club, Wisla Krakow.
It is understood the move for Gabri collapsed because of the Spaniard's injury record.
Gabri had been sidelined for eight months following knee surgery. West Ham were keen to sign him on a short term deal until his fitness was proved, while the player wanted a three-year contract straight away.
Gabri will now remain at Barcelona until the end of the season before becoming a free agent.
Pardew is expected to give his reaction to the signing later on Wednesday - but he will be delighted to have landed Scaloni, who brings a wealth of Champions League experience to the club.
Scaloni joins a West Ham squad already bolstered during the January transfer window by the £7million club record signing of striker Dean Ashton from Norwich.
Ashton is available to play for the Hammers in tonight's Barclays Premiership clash with Arsenal at Highbury.
But he faces stiff competition for a place in the starting XI from Bobby Zamora, who has scored three goals in his last four games, Marlon Harewood and Teddy Sheringham.