The Argentina global was ruled out his country's must-win World Cup Qualifier against Ecuador after a taxi in which he was travelling in Amsterdam struck a pillar.
Aguero told broadcaster TyC Sport: "The money isn't a problem here, but I think Messi, like Ronaldo, is a player who is a symbol of their club and it's hard for them to leave".
"But Leo, just like other players like Ronaldo, are symbols of their clubs and it's hard to leave not just to City but to other clubs that also have the money".
The 29-year-old, though, has appeared to indicate he could be in selection content for the match against Stoke City on Saturday, while he also hit back at those criticising him for going to Amsterdam on his days off.
Aguero is now recovering from injury after fracturing ribs in a vehicle crash in Amsterdam last week.
"When a player has a free day at Manchester City, most of the players go to London, others to Italy, some to Spain", he said.
"I left for nearly two days and went back to the airport and then got into that accident".
"But he's a symbol of his club and I think it would be rather hard".
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"Today I have trained normally, but not yet with the group".
"I would love to see Messi join - who wouldn't love to have Leo in his team?"