Visibly dejected and in tears after Lucas Biglia's spot-kick was saved as Argentina crashed to a penalty shoot-out loss to Chile in last month's Copa America Centenario final, Messi - who missed from the spot himself - publicly announced his plan to walk away from international football.
Messi's announcement came after a third consecutive defeat in a major final, fourth in total, and 113 appearances for Argentina since debuting in 2005.
Many past and present players feel Messi's comments were in the heat of the moment, with the 29-year-old five-time Ballon d'Or winner tipped to return for Argentina's 2018 World Cup qualifying campaign.
Mendieta, who spent a season on loan at Barca in 2002-03 while he earned 40 caps for Spain, believes the pressure of trying to end a 23-year wait for a major title came to the fore, telling Omnisport: "When you come out after losing a game like that, in the heat of the moment you might say things you're not really thinking.
"I mean it goes through your head because he just lost a third final in a row, fourth in total, with Argentina.
"The anxiety for not only him but the entire country to win a major trophy was massive.
"For so long, living with this pressure and anxiety of winning, it's not easy to deal with.
"I think personally it was the heat of the moment. Messi loves football too much and his country too much not to play again.
"I'm sure after holidays he will think differently."
Gerardo Martino has since resigned as Argentina coach, with the South American giants set to resume their World Cup qualifying campaign against Uruguay on September 1.