Mane, 27, helped spearhead the Reds' charge to their first UEFA Champions League title since 2005 earlier this year, as well as finishing runner-up with Senegal in the 2019 Africa Cup of Nations.
Barcelona talisman Messi, 32, clinched a record-breaking sixth Ballon d'Or in Paris, France, and told Canal+ (h/t Goal's Kunle Fayiga) Mane was his top pick to win The Best FIFA Men's Player award earlier this year:
"It’s a shame to see Mane finish in fourth place.
"But I think there have been a lot of great players this year. That's why it was difficult to choose a particular player. But I chose Sadio Mane because he's a player that I like.
"Mane achieved a great year that was exceptional for the entire Liverpool team. That's why I chose him. I repeat, there were a lot of very great players this year, so the choice was difficult."
The Ballon d'Or is an annual awards ceremony organised by France Football, which is decided by votes from journalists across the globe, whereas FIFA's equivalent award is decided with player input.
Messi won for the first time in four years to move clear of rival and five-time Ballon d'Or winner Cristiano Ronaldo, edging Mane's Liverpool team-mate, Virgil van Dijk, by a narrow margin:
Mane took to social media and explained his absence from Monday's ceremony was due to the Merseyside derby against Everton on Wednesday, though Van Dijk was there:
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Sadio Mané on missing the Ballon D’Or ceremony: “My schedule didn’t allow me to be with you tonight as I have a match on Wednesday but congratulations to the winner, see you next year. Hopefully to win it! Inshallah!” Doesn’t van Dijk have a match too? https://t.co/lFcNZNpekb
Juventus superstar Ronaldo finished third in the vote and has featured on the Ballon d'Or podium each year since 2011. This was the first time since 2010 that he's failed to crack the top two.
It looked as though the extra rest served Mane well prior to the clash with Everton at Anfield on Wednesday, when he dazzled with two assists and one goal in a 5-2 drubbing:
Liverpool team-mates Mohamed Salah (fifth) and Alisson Becker (seventh) also broke into the top 10 of this year's Ballon d'Or vote, which highlights the quality on Merseyside.
Messi got a close-up look at Mane's talent when Barcelona lost a 3-0 first-leg lead in last season's Champions League semi-finals, crumbling 4-3 on aggregate to the eventual champions.
Mane didn't manage to score or assist in that 4-0 second-leg turnaround at Anfield, but the quality he demonstrated across 2019 was enough to convince record-breaker Messi of his talent.