Chelsea took control of Group E after Jorginho's penalty and Pierre-Emerick Aubameyang's strike gave them their first win on Italian soil.
The Blues were given a helping hand when Chelsea academy graduate Fikayo Tomori was sent off in the 18th minute for the hosts for a tug on Mount, resulting in the penalty which Jorginho dispatched.
But Mount feels his former teammate was harshly dealt with and should have been allowed to continue playing.
In an interview with Chelsea's official website, Mount said: "I was probably a bit surprised [with the decision] at the time because I've still gone through and had a shot.
"I felt him [Tomori] trying to pull me back but I was running to goal so I wasn't going to go down. I carried on going, didn't score and then obviously the ref blew up and gave a pen straight away."
"He's obviously my mate, I've known Fik for a very long time, and I felt for him in that situation, I was gutted for him. I don't think it was a sending-off," Mount added.
"You still want to be playing 11 v 11 and going at it with two good teams, so it maybe ruined the game a bit. It was massive for us and we obviously wanted to win the game, which we did."
Chelsea will look to seal their place in the knockout rounds when they travel to RB Salzburg in a fortnight.
