Enzo Pérez's call-up as a last-minute replacement in the Argentina squad has made the Albiceleste the oldest team at a second World Cup in a row, with an average age of 29 years, six months and 24 days.
River Plate midfielder Pérez, 32, flew out to Russia after 25-year-old Manuel Lanzini injured his knee, pushing Argentina past Costa Rica as the oldest squad by a single day.
The Albiceleste also had the oldest squad in Brazil four years ago, when they finished as runners-up to Germany, with an average age of 28 years, 11 months and six days.
At 36, Chelsea goalkeeper Willy Caballero is the eldest member of the squad, two years older than Javier Mascherano, while Giovani Lo Celso and Cristian Pavón are Argentina's youngest players, both 22.
Latin American sides account for the third and fourth oldest squads as well, in Mexico and Panama respectively, while Brazil are eighth out of the 32 teams.
At the other end of the scale, Nigeria, who will face Argentina in Group D, feature the youngest squad at an overall age of 25 years and 11 months.
The national team squad has become quite the attraction in Russia, with around 400-500 eager fans turning out to catch a glimpse of Lionel Messi and his team-mates.
At an opening training session on Monday, a particularly affectionate welcome was reserved for the Barcelona forward, as hordes of adoring young supporters chanted "Messi, Messi" on his way out for an hour-long practice.
After several days of chilly temperatures in the Russian capital, overcast skies gave way to sunshine, with excited locals packing a temporary stand in Bronnitsy, southeast of Moscow, to follow the action.
The odd Messi mask was spotted in the crowd, while others waved Barcelona flags, as well as those of Argentina.
The five-time Ballon d'Or winner was then mobbed by dozens of youngsters at the end of the session as players stopped to sign autographs.
Ernesto Lagorio, Argentina's ambassador to Russia, was at the session at the sprawling training centre, used by several Russian national sports teams, on the banks of the River Moscow.
"We came to see our national team, it's the first acquaintance with them, it's been great," Lagorio told AFP.
"We've already been to Bronnitsy several times, we've worked a lot with the authorities and the mayor. He's helped us a lot, it's been in the works for several months."
Asked whether he would be attending matches, he replied: "I hope to show up until the final match in July."