Pickford came surging out of his goal in the early stages of the match and clattered into Liverpool defender Van Dijk in a scissors motion, crunching the outstretched knee of the Dutchman.
Van Dijk immediately collapsed in a heap and needed extensive treatment in the area, before having no option but to leave the field.
Mason, who's career was cut short following a life-threatening head injury, declared on social media: "Just seen the Pickford tackle.
"Could end a career that, terrible terrible tackle! He has done it before and will do again!"
"If that happens in the middle of the pitch they sometimes get away with it because they have to fly out. If that happens in the middle of the pitch it's an instant red card."
Everton icon Leon Osman, also featuring as a studio pundit, added: '"It's an absolutely horrendous tackle and we don't want to see it in the game. It's a career ender. But it actually changed the momentum of the game."