Real Madrid have signed Boca Juniors midfielder Fernando Gago for £14m.
The 20-year-old's arrival will heighten speculation over David Beckham's future in the Spanish capital.
Beckham, 31, has struggled to hold down a place in the Real team this season as coach Fabio Capello has attempted to overhaul the La Liga's aging squad.
Gago has signed on a six-and-a-half year deal and follows River Plate striker Gonzalo Higuain, 19, in moving from South America to Spain.
Higuain, who was born in France and raised in Argentina and is yet to commit his international career to either country, moved in a £9m deal.
Their arrival follows the signing of Brazilian full-back Marcelo earlier in the season as a potential long-term replacement for Roberto Carlos.
Gago, who has been dubbed his country's heir to former Real star Fernando Redondo, has been tipped to play in either central midfield or on the right flank.
It heightens pressure on Beckham who has spent much of the first part of the Spanish season on the bench.
While the former England captain did start Real's last match, a 3-0 defeat to Recreativo Huelva left them five points off top spot in third place.
And Beckham has suffered further ignominy by being asked to play in a meaningless pre-Christmas friendly against Atletico Madrid while other big-name players have been excused early for the festive season.