The official was kept busy at Anfield on Saturday as the most volatile fixture in Premier League history produced two more red cards.
The dismissals of Sotirios Kyrgiakos and Steven Pienaar means there have now been 19 red cards in 36 Premier League derby showdowns.
"It was a very hard job for the referee because the players did not help him," he said.
"It was a hard game with a lot of tackles but this is the way it is in derby matches, they don't want to lose and we don't want to lose. Sometimes you can see some hard tackles because of this.
"Soto (Kyrgiakos) said to us that he went for the ball, maybe he went in the wrong way but he went for the ball."
The red card for Kyrgiakos saw Mascherano pressed into service as a makeshift right-back.