Asked if there was anything wrong with Tevez's attitude during his last year, Joorabchian said: "Absolutely not, he was desperate to play. He scored 15 goals with seven assists, his record was superb. Every time, he was available for every game bar the three he missed through injury.
"I think the person's professionalism to be questioned is Gary Neville because he didn't do his homework on Carlos' career or as a reporter to say why Tevez wasn't [professional]. He never made any phone calls, he never asked the question of me or anyone to know what has happened. He just makes comments time and time again.
"By saying things like that, he is putting a mark on the back of a player who has won double or triple the trophies he has ever won.
"Carlos has won trophies in every single league he has ever played in, he has been nominated as player of the year in South America more than any other player in history and now, at the age of 34, he's just won the league and scored the winning goal with Boca Juniors again."
It was reported that Tevez refused to join United, who wanted to exercise their option to sign the Argentine permanently.
But Joorabchian has denied those claims.
He said: "Generally speaking, Gary Neville spoke about professionalism, the treatment table and he spoke about people being in his [Tevez's] ear. What he doesn't understand is, and this is when a reporter should have the correct information, no matter who was in his ear, no matter who was speaking to him, if Man United had wanted to exercise an option, all they had to do was sign a paper and send it to the Premier League.
"He wanted to stay at Man United right after Moscow and winning the Champions League when he came on and he knew what he had to do. He had to get under Chelsea's skin, he got [Didier] Drogba sent off and they ended up on penalties, which they won, and it was a great moment.
"They came back and him, Rooney and Ronaldo had a great combination going forward, they were very happy, but Man United didn't exercise the option. It was as simple as that.
"Gary Neville is speaking about people being in his ear as if Tevez decided at that point to leave during that year, but it was Man United who didn't exercise that option. Tevez only decided after the option had expired that he had been sitting there for nine months and no one has exercised the option."