Amorim stated last week that Antony failed to find consistency in England due to the physical demands of the Premier League.
But agent Junior Pedroso told Marca: "We respect the opinion of coach Ruben Amorim, but we completely disagree with his analysis. To attribute Antony's lack of success at Manchester United solely to the question of physicality is a very superficial argument and does not reflect reality.
"The truth is that Antony has not had enough prominence or the confidence necessary to play his best football. Of the 15 games in which Amorim managed Manchester United, he only used Antony in nine, with a total of 252 minutes played. This represents only 18.6% of the total possible minutes (1,350 minutes). How can you judge an athlete without a minimum sequence to prove his worth?"
Pedroso continued: "The manager's statement, although perhaps it was not his intention, ends up devaluing La Liga and the Spanish competitions. Spanish football has one of the most competitive leagues in the world, with top-level teams that constantly compete in the final stages of the Champions League and the Europa League.
"The reality is that Antony, since he arrived at Real Betis, has become one of the best players in the team and in the competition itself, demonstrating his full potential when given the right conditions to develop his game. This highlights that the problem was not the physicality, but the context and the way he was managed in Manchester.
"Many players who do not prosper at United find success at other clubs, which leads us to wonder if the problem really lies with the players."