Same with Mancini at City. City as a whole was absolutely terrible in Europe during Tevez's time there. He just wasn't provided service. And I'm pretty sure his one season there as he only really played for them in 1 CL season, they had that group of death. Real Madrid< Dortmund, Ajax. Tevez only started 3 games, and was a sub in 2 others. So he played in 6 games in total in CL and only 3 as a starter for City. @Hist
His European performance for city is much more a case of hardly any playing time in Europe, rather than poor performance.
Last season for Juve was a mess. Certainly. But I'd say that was in part again, Juve as a whole was a mess in Europe. Now that Juve is performing, Tevez is performing. This is the first time he's played in CL since ManU on a team that actually looks decent in Europe.