I think it's very clear that this is the 'Essien' type player. And I can understand clearly why Herrera has not cemented himself under Mourinho after re-watching Essien's best games. And also why Pogba has not cemented himself in that role. And also why Fred can fill that role. Of course, I am in no way saying Fred will be as good as Essien, but that's not a problem because Pogba can make up in the technical department very easily.
There is a simplicity required for that role, because it is always about taking advantage of the transition. You have to be quick to pass and quick to dribble. Pogba obviously isn't that type of player, he uses the ball to commit players and beat them through skill and physicality. Herrera is that type of player however, he does not have the correct skill set when passing or dribbling to do it. He mainly has one pass in his locker (the hard pass into space) and his dribbling doesn't cover a lot of distance.
Fred is a very simple player, and his dribbling is very good. I know it's a bit cliche to compare players, but he brings a lot of the same qualities as Kante. He doesn't do anything amazing, but does the basics really well. Covering spaces, pressing the ball, tackling from the blind spot, dribbling into space, releasing the ball. He's a percentage player, he's not going to do something amazing (except on free kicks because he's good at those) but he'll make the right decision most of the time. He's an anti-flair player.