Captain Messi was injured for Argentina’s first four qualifiers last year for the 2018 finals in Russia and the team suffered in his absence.
They took just five points from those games to sit outside the qualifying berths in sixth place in the South American group.
“Messi’s presence is calming, motivating and always necessary,” Martino told a news conference on Wednesday before leaving with his squad for Santiago.
He faces a difficult decision in who to pick out of Sergio Aguero and Gonzalo Higuain, both in fine club form, to lead the attack in the neighbours’ first meeting since Chile beat Argentina on penalties in last year’s Copa America final.
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Napoli's Higuain and Manchester City's Aguero played together in a four-man attack that included Messi and Angel Di Maria in several of the 2014 World Cup qualifiers.
Yet Martino, who took over after the tournament in Brazil, has always favoured one or the other.
“We have two of the world’s five best centre-forwards so, given how we play, I’m going to be unfair to one,” Martino said. “Whoever plays will feel good, whoever doesn’t will feel bad.”
Martino also called up Paulo Dybala, who is a fast emerging talent, but the Juventus striker had to withdraw through injury from the Chile match and next Tuesday’s qualifier at home to Bolivia.
Argentina are seven points behind leaders Ecuador, who upset Martino’s side 2-0 in their opening qualifier in Buenos Aires in October, four behind Uruguay and two behind Brazil, Paraguay and Chile.
“Today the table shows we’re out of the World Cup so our responsibility is to win both matches to get into the group that would qualify,” Martino said.
Chile's new coach Juan Antonio Pizzi said they will not play for a draw.
“No footballer or member of Argentina’s coaching staff is going to settle for a draw, neither will we,” Pizzi told reporters in Santiago.
“I’m aware we’re going to face one of the best national teams in the world but I’m confident. We will fight to win the match.”
After 18 rounds of matches, the top four teams in the 10-nation South American group qualify for the finals while the fifth goes into an intercontinental playoff.
(Reporting by Rex Gowar; Editing by Toby Davis)
