Lionel Scaloni will not alter his principles, insisting that is "non-negotiable", as he tries to plot a route past Mexico and keep Argentina's World Cup hopes alive.

The South American champions were stunned 2-1 by Saudi Arabia in their opening game, plunging their qualification for the knockout phase from Group C into unexpected doubt.

Another defeat at the hands of Mexico, coached by Argentinian Tata Martino, could prove fatal but Scaloni dismissed any notion of a change in playing style from his team.

He said: "We watched the game back [against Saudi Arabia] but now we are thinking about Mexico which will be entirely different.

"But the way we will play will be similar, we won't change our style due to what happened on Tuesday, that's clear. Mexico are an excellent team, an offensive team with a great coach. But we have a style that is non-negotiable.

"We might have taken a blow in the opening match but we need to stick to our guns and approach it in the same way.

"When you have a blow you have to bounce back and the squad is ready to do that. We know there is a full country behind us and the fans can take confidence that the team will break their backs until the very last seconds they are on the pitch so we can reverse this difficult situation."

Scaloni confirmed captain Lionel Messi has no issues ahead of the encounter at Lusail Stadium.

"He trained well and he's feeling well," he added. "More than ever we need everyone, and I am sure everything will play out. We have no issues with his physical level."

Inter striker Lautaro Martinez acknowledged Saturday's game is "like a final", but is confident the team can cope with the levels of expectation.

He said: "Tomorrow is a big match for us. It's like a final because we need to win. It will be a very important match for our future but we've proved that we have the players and the quality and for a game like this that will be key.

"There is no pressure because we rely on our work. We are confident, have trust in our technical staff and every player. We are keeping calm and confident and will do everything for our fans."

Martino, who also coached Argentina from August 2014 to July 2016, was asked how he feels about potentially robbing Messi of a final chance to win the World Cup, replying: "What would you do if you were in my place? I hope Mexico win, there's no other answer. I will do my utmost for a Mexico win."

Mexico played out a drab goalless draw with Poland in their opener and Martino was eager to stress there was plenty at stake for his team too.

"I don't think the needs [for the teams] are that different," he added. "The game is key for us as well, we only have one point. We will try to play with our own ideas but we are playing a powerful team. When we saw Argentina in our group, we did not see a situation like we have.

"After Argentina's defeat, this has become a key match, especially as we also didn't have a positive result. If we get a positive result here, we might be in a position to qualify for the next round."