His work ethic was fine but the quality in his game definitely went up a notch at City. Although my main point is that I can never get on board with having fond memories of a player who acted like such a dick and was a much more impactful player for City than he ever was for us (whatever the reasons behind this)
It's true but it has a clear explanation, Tevez ain't a second fiddle player, for the good and for the bad.
He wanted so bad to be a United player that he adapted to a "secondary role" to not cause any disruption, it worked wonders and because Fergie didn't think much of him and tried to paid him less and late, everything got worse and with a personality like Tevez, that ship was going to sink (worse when he had that awuful Kia and cia managing his bizzness). Fergie in this case read really bad with whom he was dealing, even if he thought Tevez wasn't exactly his cup of tea as a player.
Many United players from that period, bar Neville and mostly those who still are kind of even afraid of Fergie, has said that they didn't got the Club and Fergie's move. To this day Wayne names him his prefferred partner (it was like having Twins in the pitch) and his problems with the Club kind of started when he faced the Club asking what was happening loosing CR and Tevez so fast. THey knew that not only Tevez was great for them but that he was going to be quite a problem facing him playing for another team...when he went to City, the scenario was even worse.
Tevez is Tevez, he ain't easy, he got bored at some point everywhere, but perhaps the only time in his carreer that he actually low his head was with United, he certainly didn't feel wanted by the Club and Fergie, or better said, he didn't felt appreciated as a player.
A pity because that United was the type of team a Club should hold as much as they can, the right combination of skills and personality a United team must have.
To make it worse Tevez was the final Catalyst that started what City has become today.
The funny thing is that his problems with Fergie and Mancini, were the issues that the Press used to "kill" him and cemented his kind of bad image, while in reality on both ocassions he was more in the right.
He did worse stuff when he left Boca, how he left Corinthians, how he even left Juve to at first come back to Boca for sentimental reasons (Juve doidn't wanted to loose him) and went to China... those were their truly Tevez problematic moments, with Fergie and Mancio, it was more about two stubborn managers pushing his buttons with not much reason behind it and later having toi deal with Carlitos I don't give a fvck attitude, I do it my way.