Thiago Silva labelled Lionel Messi the greatest player of all-time ahead of Brazil's Copa America semi-final showdown against Argentina.

Messi has been criticised after a quieter Copa America campaign, although Argentina are into the last four and face their rivals in Belo Horizonte on Tuesday.

Silva said there was no doubt the Barcelona star, 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 told a news conference on Saturday.

"But now, it's Brazil and Argentina. We'll leave it to admire him in other games ahead."

Brazil have endured some difficulties as Copa hosts, booed repeatedly by their fans and needing penalties to edge past Paraguay in the quarter-finals, and now they face 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, 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 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."