Cavani plays as a striker for Napoli but with Luis Suarez and Diego Forlan in the Uruguayan front-line, he drops to a deeper position for the national side.
He spent much of Monday's opening Group C match against Peru wide on the right, feeding the two forwards in the 1-1 draw.
Asked in a news conference which position he preferred, he said the statistics spoke for themselves.
"In Napoli I've had a great year in the position I was playing, but we all know that in the national side the only position in which it's been possible for me to play isn't the same," he said.
"They're two different things. I have to play a different role here. I'm ready to do it, and to give my all, but it's normal that sometimes you get to the end of a match and you're left with an urge to have done more."
Cavani scored 33 goals in 47 matches last season with Napoli, 26 of them in the league. He has scored nine times in 28 matches for Uruguay, including in their World Cup third-place playoff defeat by Germany last year.
The 24-year-old said he was possibly feeling the impact of a tough season in Italy.
"The truth is that we're not machines and we're not designed to play so many matches," he said.
"I think the manager's done everything possible to have us in top shape for this Copa America, so I'll try to give everything I can, and I think that after it's over we can come to conclusions about what kind of physical state we're in."
Cavani is likely to start Uruguay's second Copa match against Chile in Mendoza on Friday.
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