Lionel Messi's return from injury has "reinvigorated" the Argentina side, manager Gerardo Martino said.
Messi missed the Albiceleste's opening game of the Copa America Centenario, a 2-1 victory against holders Chile, before coming as a substitute in the second, to score a hat trick in the 5-0 win against Panama.
In the subsequent matches Bolivia have been beaten 3-0 and Venezuela 4-1 as Argentina booked a place against the United States in the semifinals of the tournament and Martino thinks Messi's contribution has been vital.
"He knows that he's a game-changing player," Martino said. "Everybody's trying to cancel him. But he knows when to play one against one. He knows when to pass the ball to other players. There may be times when he lets some other player take advantage of this.
"I'm pleased by the way he has recovered from his injury. He's reinvigorated the team. I'm very happy to have him good shape, especially heading into the semifinals."
Argentina have reached and lost two major finals during Martino's three years in charge and are favourites to make it to another, but Martino has played down the significance of winning silverware instead pointing to the side's development as his main source of pride.
He said: "I am proud, the last three years I have been in charge, they have played three tournaments, and no matter what they will have played 19 games.
"Most of the games they have played very well, but in two of them not very well but still they come full of hope and lots of confidence.
"It's not easy for a team that came as far in previous tournaments to come as far in this one. I feel we are growing, and that really fills me with pride."
Martino chose to replace Gonzalo Higuain with Sergio Aguero when he was on a hat trick, and stressed the importance of keeping both strikers happy.
He said: "We have two strikers who are really exceptional. I cannot repeat it enough, I really feel this. People in Argentina have trouble accepting it with the quality of players we have, we have two No. 9s.
"We try to boost their confidence as much as possible, even though it's difficult when not both of them can play. We give them confidence because either or both of them can really be decisive in a tournament, especially if we're chasing a game."