A man who found the target on 51 occasions for his club in 2018-19 was, however, unable to add another Copa del Rey crown to a 10th Spanish league title.
Messi has the opportunity to make amends for that setback this summer when heading away with his country.
The 31-year-old is chasing down a first senior international honour and will arrive in Brazil for the 2019 Copa with three previous final defeats in the competition weighing on his mind.
Aguero believes an iconic colleague is determined to lead Argentina’s charge for major silverware, telling reporters of Messi’s mindset: “No one likes to lose.
“Messi has been feeling bad for the last competitions, the Champions League and the Copa del Rey.
“But he is a great man, he has experience he knows that football is like that, that it is about joy and sometimes it is about sadness and maybe anger.
"He knows it better that anyone.
“He arrived well in here and we all know how motivated he is when he comes here and the happiness he transmits is something that is fundamental for us.
“We know that he loves the national team a lot and everyone should realise that.”
Messi has faced criticism at times for his performances with Argentina, with a man who boasts 129 caps to his name often struggling to hit the heights he does at Barcelona.
Those in the Albiceleste camp do, however, have full faith in him, with national coach Lionel Scaloni saying of his captain: “Leo needs a team and the team needs him. That must be normal.
“Here he needs his companions. And we all need a team, commitment, the desire to win, to do something, always talking and thinking in plural.
“Messi is the first to know, [that] he needs his team-mates.”
Argentina will open their Copa America campaign against Colombia on June 15, before then taking on Paraguay and Qatar in their other Group B fixtures.