After losing at the same stage to the Argentinians in Germany four years ago the Mexicans need every bit of firepower they can get against a team which has a wealth of attacking talent but which is rather more suspect at the back.
Arsenal youngster Vela had to go off after half an hour of last week's 2-0 win over France at Polokwane after feeling a sharp hamstring pain which doctors said would require ten days on the sidelines.
That means he could just be back in the frame for the Johannesburg showdown at Soccer City after he was forced to sit out Tuesday's loss to Group A winners Uruguay.
Vela trained apart from the remainder of the squad on Thursday as he went through a special session to get him back into contention for Javier Aguirre's men, having the previous day looked to be more or less over the injury as he jogged with his teammates for some 2km around the training track.
Aguirre had them running around again on Thursday as reporters speculated the tactic might either be to beef up their stamina to face the dangerous Argentinians or else a punishment for what he termed "a poor attitude" in the loss to Uruguay.
"There were different factors at play in the Uruguay game and if there was something lacking there then we have to up the tempo a little," said midfielder Gerardo Torrado.
"Every game is different. We must play aggressively and look to put their goalkeeper under pressure," added Torrado, who is one of three captains in the El Tri squad along with Barcelona defender Rafa Marquez and veteran Cuauhtemoc Blanco.
"We have what it takes to beat them - but we have to go out in the right frame of mind and do it on the pitch," Torrado concluded.