Some defensive partnerships are built on months of training. Mexico's is built on a friendship that began in childhood.

Centre-backs Cesar Montes and Johan Vasquez have known each other since they were 10, growing up in the same region and following remarkably similar paths through Mexican football. Now, that lifelong understanding has become the foundation of a Mexico defence that has yet to concede a goal at the FIFA World Cup.

Ahead of El Tri's Round of 16 meeting with England, Vasquez revealed how a friendship forged in the youth ranks has evolved into one of the tournament's most formidable defensive partnerships.

"I think I was about 10 or 11 when I first saw him. We met at Pachuca, and that's where we realised we were from the same state, the same region, the same area," Vasquez told FIFA.

Their journeys continued to overlap. They reunited at Cimarrones de Sonora, crossed paths again at Monterrey and eventually became team-mates for the national side.

"We met again when we were at Cimarrones de Sonora, then at Monterrey, and now we're both playing for the national team," Vasquez said.

Being from the same place, you tend to look after each other. I would move to a new club and wouldn't know any of the other guys. You end up gravitating towards the person closest to where you're from....We've been friends for many years and know each other very well.

Johan Vasquez, Mexico defender

Their shared roots have made adapting to new environments much easier.

"Being from the same place, you tend to look after each other. I would move to a new club and wouldn't know any of the other guys. You end up gravitating towards the person closest to where you're from. When I first arrived, he welcomed me and helped me with lots of things. It felt familiar. We've been friends for many years and know each other very well."

Their bond was further strengthened when they helped Mexico win the bronze medal at the Tokyo Olympics, a squad that also featured several players who graduated from the Cimarrones youth system and now form the spine of the national team.

"Quite a few came through the system. We've become a family in the national team. We've known each other and played together for years. That's the key," Vasquez said.

"At the Olympics we won a historic bronze medal. It's one of the best competitions I've ever played in for many reasons."

That chemistry has translated into results on the biggest stage. After four matches at the World Cup, Mexico remain the only team yet to concede, with Montes and Vasquez at the heart of a defence that has frustrated every opponent.

Vasquez, however, was quick to credit the collective effort rather than the back four alone.

"I think it's a beautiful thing to be able to give the team a sense of security and for the team to trust you. We try to do our job, but just because you haven't conceded a goal doesn't mean everything is perfect defensively.

We've known each other for a long time, and we know each other's limits. I think that's what makes us such a great defence.

Johan Vasquez, Mexico defender

"There have been times when a team-mate, the goalkeeper or someone else has saved us, and all the credit goes to the defence. But it's really a collective effort.

"We're all aware of the different phases of the game, we've known each other for a long time, and we know each other's limits. I think that's what makes us such a great defence."

For Mexico, the numbers tell one story: four matches, four clean sheets.

The friendship between Montes and Vasquez tells the other. 

Long before they became the backbone of Mexico's World Cup defence, they were simply two boys chasing the same dream together.