The Inter Miami star was left out of the matchday squad for their World Cup qualifying clash with Bolivia after being brought off late in the game against Ecuador last Thursday.
But that didn't stop Messi from enjoying the action as Argentina secured a 3-0 victory, with Chelsea star Fernandez giving them the lead.
Playing in La Paz - the world's highest capital city at 3,625 meters above sea level - the 22-year-old slotted home before wheeling away in celebration, with the TV camera then panning to the 36-year-old who was grinning from ear to ear at what he had just watched.
If it was the goal of Fernandez that impressed Messi, football's GOAT will have been relieved to see Cristian Romero escape without serious injury.
The Tottenham defender was on the receiving end of an awful challenge from Roberto Fernandez as a late challenge saw him stand on the centre backs ankle.
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While Fernandez was sent off for the offence, Romero was lucky to escape without a broken ankle.
Messi made headlines after naming the Tottenham star as the best defender in the world, something that Ange Postecoglou couldn't dispute during his appearance on White And Jordan.
"I wouldn't argue with Messi," Postecoglou exclusively told talkSPORT. "I'll tell you what, I wouldn't like to play against him [Romero].
"Most of the boys don't like to train against him.
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"He's a real competitor and I love that about him.
"Whether it's training or a game, what you see is what you get with Romero."