Argentina are looking to put their shock 2-1 opening defeat by Saudi Arabia behind them as they prepare for their World Cup Group C match against Mexico on Saturday, a game they now feel they absolutely must win.

The Argentines are also hoping to restore their status as one of the tournament favourites against goal-shy Mexico.

"It will be like a final for us because it is a match that could define our faith in this World Cup," forward Lautaro Martinez told a news conference on Friday.

"It was a heavy blow to our morale (losing to Saudi Arabia) but we are a strong group that is very united.

"We need to stay calm, recover and think about what's coming. And what's coming is Mexico, so we have to focus on getting the win no matter what."

Lautaro said Argentina dominated the match against the Saudis and did not deserve to lose, having three goals ruled out for close offside calls by VAR.

Now they will face Mexico's low-scoring, injury-hit squad that bore out the pre-tournament pessimism in their first game, drawing 0-0 against Poland and only avoiding defeat thanks to a stunning save from veteran goalkeeper Guillermo Ochoa.

"We are very optimistic and I think we lost because of small details, due to our own mistakes. We have studied our next rival and I think we are ready," Lautaro said.

Coach Lionel Scaloni said that Lionel Messi is fit and ready to play despite reports of a possible ankle injury and that he believes his squad has what it take to rebound from their opening defeat.

"When you are knocked out you have to get up, and my players are more than capable of doing so," Scaloni said.

"We will not change the way we play because of the loss to Saudi Arabia. I can make a change or two in the selection but not in our system, that is not in question.

"This group will leave everything they've got on the pitch to recover from that heavy blow."