Brasilia: La Albiceleste can secure their place at World Cup 2014 in Brazil with a win at River Plate`s Monumental Stadium in Buenos Aires on June 7.
The Argentina coach has one big injury concern in the shape of Messi, who was called up to the national side despite struggling with a hamstring injury since April.
And the 25-year-old was a notable absentee for Sabella`s final training session before the clash, prompting concerns that the Barcelona star will be limited to a cameo role at best for Friday`s game.
"If Messi can`t play, the alternative is Walter Montillo," the Argentina coach told reporters at a press conference.
“His leg is OK. He looks quick and capable of taking on defenders, but we need to see how fit he is after so long without playing. The doubt is due to his inactivity.
"We will make the decision this afternoon; we will do a little very light training session to see how everyone in the squad is in general, particularly Messi."
Messi`s importance to Argentina is obvious, with Celta Vigo midfielder Augusto Fernandez admitting that even a half-fit version of the Barcelona man can help the team.
“He can make the difference with one leg, that`s why we want him to play,” said the 27-year-old.
The three time Ballon d`Or winner`s possible replacement, Montillo, currently plays in Brazil with Santos and has made four appearances for the national team.