Messi has been criticised after a quiet Copa America campaign, although Argentina is into the last four and faces its rival Brazil in Belo Horizonte on Wednesday (AEST).
Thiago Silva said there was no doubt the Barcelona star, who is a five-time Ballon d'Or winner, deserved to be considered the best player ever.
"For me, Messi is the greatest player in history, the greatest player I've ever seen," the Paris Saint-Germain defender said.
"But now, it's Brazil and Argentina. We'll leave it to admire him in other games ahead."
The Selecao has also endured some difficulties as Copa host, having been booed repeatedly by its fans and needing penalties to edge past Paraguay in the quarter-finals, and now it faces a Messi-led Argentina side growing in confidence after back-to-back wins.
While Messi has scored just once in four games at the tournament, Thiago Silva praised the forward's ability to produce moments of magic.
"Every time we face each other, whether in the national team or in the [UEFA] Champions League, it's very difficult to face him," he said.
"No matter how much you study, you will never understand the quality he has and the difference he can make.
"At certain times, he pulls something else out of the hat that you cannot imagine. That's his difference.
"As a centre-back you have to study all the possibilities. We know he always pulls left, but many times he pulls right."