Veteran skipper Rafael Marquez has warned Mexico they face their toughest challenge yet as they attempt to book their place in the second round of the World Cup finals.

The 35-year-old former Barcelona defender's claim may raise eyebrows given that Los Aztecas, following a narrow victory over Cameroon, have already encountered hosts Brazil and emerged with a 0-0 draw which has left qualification firmly in their own hands.

But as they prepare for their Group A showdown with Croatia in Recife on Monday, Marquez insists they can leave nothing to chance.

He told www.fifa.com: "This is our biggest game. We know we have to keep the momentum going.

"We worked so hard in our last two games and we don't want to throw it all away against Croatia.

"We have always known we were going to face tough opponents. Croatia have loads of very talented players.

"They have got very quick wingers who can get to the byline and put the ball in the box. They have also got a lethal striker and some of the best central midfielders around.

"They are a great team, so it won't be easy. We will have to give our best to get at least a point and move on to the next phase."

The equation is simple for the Mexicans: avoid defeat and they will progress to face either Holland or Chile in the next phase of the competition.

However, defeat would see the Croatians leapfrog them and that, coupled with anything other than a heavy reverse for Brazil at the hands of pointless Cameroon, would send them home.

Marquez, leading his country for the fourth time at the World Cup finals, said: "If you take a look at the quality of the teams we have faced, it shows how difficult and tough a task we have had.

"And though we are not there yet, we are close to taking an important step. Keeping clean sheets has been key for us, and we are determined to keep that going."

Croatia boss Niko Kovac will head into the game knowing victory represents his side's only realistic chance of making it to the knockout stage with Brazil and Mexico both currently a point better off.

However, he will not take immediate risks in his pursuit of a priceless win.

Kovac told the Croatian Football Federation's official website, www.hns-cff.hr: "I know what we need, but we have 90 minutes.

"From the first minute, we will try to impose our rhythm because we make it easier for the early goal. But we will be patient.

"I think we have quality and we have enough players to trouble Mexican defence, and as much as we look at them, so they will have to watch us."