The superstar forwards spent four years playing alongside each other at Barcelona and formed one of the most fearsome attacking tridents in history with Luis Suarez.
They forged a strong bond at Camp Nou which continued even after Neymar sealed a world-record £198million transfer to Paris Saint-Germain in 2017.
But the 29-year-old insists there can be no room for sentimentality as he faces off with Messi at the Maracana in the early hours of Sunday morning, with both players searching for their first Copa America triumph.
“Messi is, as I’ve always said, the best player I’ve ever seen play and he’s a great friend, but now we’re in a final, we’re rivals,” said Neymar.
“I want to win and I really want to win this title, which would be my first Copa America.
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“Messi has been looking for his first title with the national team for many years, and every time we [Brazil] are not present at the tournament, I cheered for him. That’s what I’ve been cheering for in the 2014 World Cup final, when he faced Germany.
“Now Brazil is in the dispute, so our friendship is on the line. The respect between us is still great but only one can win.
“When you’re friends with someone, it’s hard to forget the friendship you have – but for example when you play video games with a friend, you want to beat him anyway. It’ll be the same thing on Saturday.”
Neymar missed out on Brazil’s Copa America glory in 2019 due to an ankle injury, while Messi has fallen short in three previous finals – in 2007, 2015 and 2016.
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The pair have been two of the standout performers of this summer’s tournament, with six-time Ballon d’Or-winner Messi leading the way for goals (four) and assists (five).
The Argentina captain’s brilliant performances saw his side finish top of Group A before overcoming Ecuador in the quarter-finals with a 3-0 victory and Colombia in the semi-finals after a penalty shootout.
Messi, who recently turned 34, appears entirely unfazed by the uncertainty over his future despite his Barcelona contract expiring at the end of June.
Neymar, meanwhile, has chipped in with two goals and three assists for Brazil, who finished top of Group B.
The Selecao subsequently beat Chile and Peru in the quarters and semis respectively with back-to-back 1-0 victories.
Brazil are slight favourites to win the tournament on home soil, but will be without the services of Manchester City striker Gabriel Jesus after he was handed a two-match ban for his horror tackle against Chile, prompting a furious reaction from Neymar.