The Belgian goalkeeper joined the Reds from Sunderland for around £9million in the summer of 2013 and has been the subject of ongoing criticism from many sections of the media.
Mignolet, 27, has also won over a lot of people during his time at Anfield but one person that feels he does not belong is Everton legend Southall.
"I just don't think he's a Liverpool goalie," Toffees great Southall told The Set Pieces.
"He doesn't look arrogant. He doesn't look as if he's in command of everyone. He doesn't look as if he can go a full game without making a mistake.
"I think at times he makes great saves, but at times he can't and he's nowhere near it. I look at Mignolet and I think he can have all the coaching he wants, he hasn't improved.
"His fundamental thing, his decision making, is bad."