It was a clear foul, with no effort made to play the ball, denying a goal scoring opportunity. It doesn't matter if Carvalho was covering, as two City players would have been through, and would clearly have had an advantage. In any case, it's gamesmanship to break the rules thinking all you will get is a yellow, and hardly in the spirit of the game.
The usual protests and players surrounding the referee made a mockery of the 'respect' campaign. Any other player would have been given an extended ban for a frivolous appeal. If it wasn't a red card, there should still be consequences, but there is no mechanism in place for that.
In the Champions League, a pleasing result for us. We looked tired from Saturday, but played some really good stuff here and there. Three points away from home in the bag, which substantially eases our passage. We should just need home wins to qualify.