Angel Di Maria's thigh injury has robbed Argentina of vital attacking thrust in midfield going into their World Cup showdown with the Netherlands in Sao Paulo on Wednesday.
The skilful 26-year-old went into the tournament on the back of a stunning burst of late-season form for Real Madrid and scored the extra-time goal that saw Argentina edge Switzerland 1-0 in the last 16.
AFP Sports assesses the candidates vying to replace him in coach Alejandro Sabella's starting XI for the semi-final:
It was Perez who came on when Di Maria injured himself against Belgium in the quarter-finals and the 28-year-old midfielder is the favourite to reprise the role against Holland. While he possesses neither Di Maria's speed nor audacity with the ball, he is a technically accomplished player who enjoyed a fine 2013-14 campaign with Benfica, being elected Portugal's Player of the Year. Perez also benefits from Sabella's trust, having spent two years playing under him at Estudiantes, where the two men enjoyed Copa Libertadores success in 2009.
Rodriguez has not played since being taken off at half-time of Argentina's opening game, a 2-1 win over Bosnia-Herzegovina in Rio de Janeiro. But the 33-year-old former Liverpool player is the most experienced of Di Maria's potential replacements and offers defensive industry as well as guile on either flank. The Newell's Old Boys player also possesses World Cup pedigree, having scored three goals - including a sensational match-winning volley against Mexico - at the 2006 tournament in Germany. He also played at the 2010 competition in South Africa.
A creative, left-footed midfielder, 26-year-old Alvarez is the closest thing Sabella has to a like-for-like replacement for Di Maria, but he has played for only 27 minutes at the tournament so far, as a substitute in the 3-2 win over Nigeria. The Inter Milan playmaker is not renowned for his physical robustness, but his inclusion would give Argentina more natural width in midfield.
Gago was a virtual ever-present for Argentina in qualifying, but having been brought back into the team after starting the opener against Bosnia on the bench, he was dropped for the quarter-final win over Belgium. With Javier Mascherano and Lucas Biglia expected to start, Gago's inclusion would leave Argentina with precious little attacking dynamism in central midfield, although they would look formidable defensively. The Boca Juniors midfielder's poor form in Brazil counts again him.
The left-field choice. Celta Vigo winger Fernandez, 28, has not yet made it onto the pitch in Brazil and has only nine caps to his name. But as a defensive-minded player, he would offer Argentina protection against the threat posed by Holland's dangerous left-wing-back Daley Blind.