Mucha ably deputised for injured number-one Tim Howard during the victory.
"Tim is the number one goalie, and it has been hard for Jan," Heitinga told the Liverpool Echo. "He is a great professional who trains really well.
"I have been a bit disappointed for him because he has never had a chance. I'm happy for him that he has been able to play a couple of games.
"Tim will be back soon, but it is good for Jan that he can show everyone that he is a good keeper."