The American outfit have endured a nightmare pre-season ahead of the 2024 MLS season, which starts later this month.
They succumbed to their third defeat in four pre-season tour matches in Asia on Wednesday night - losing on penalties to Japanese side Vissel Kobe.
Miami midfielder Robert Taylor missed his spot-kick in the shootout, but was given a second chance after Kobe goalkeeper Shota Arai was adjudged to be off his line.
But lightning unfortunately struck twice for the Finland international, as he blazed his effort from 12 yards high over the bar.
Cameras immediately panned to Messi on the halfway line, where he failed to contain his laughter.
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The 36-year-old was left all smiles next to ex-Barca teammate Jordi Alba - but fans weren't seeing the funny side.
Taking to social media, one X user raged: "Lionel Messi, Captain of Inter Miami laughing at his teammate missing a penalty."
Another messaged: "His contract should be terminated ASAP. Ridiculous."
A third added: "This is so sad to see, instead of encouraging and supporting his teammates, he's laughing."
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Meanwhile this supporter simply stated: "Bro has no manners."
Messi fans were also left infuriated last weekend when he was left on the bench in Inter's 4-1 win against a Hong Kong XI, with the country's government even voicing their frustration.
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Supporters booed David Beckham and jeered throughout the match, as they chanted for the World Cup winner to grace the pitch.
Their strong reaction led to Messi to defend himself in a statement, insisting he was nursing a minor injury.
He said: "Unfortunately in football things can happen in any game, that we may have an injury. It happened to me.
"I couldn't play in the Hong Kong match, and it was a shame because I always wanted to participate, I wanted to be there and even more so when it came to these matches.
"When we travelled so far and people were so excited to see our matches… I hope we can return and we play another game and I can play as I do whenever I can.
"But the truth is that it is a game that I was not able to participate."