Ex-Liverpool star Souness feels the 24-year-old is performing well below expectation and feels he is not sure what is required of him in the centre of the field.
The France global made a blistering start to his second campaign back at Old Trafford after Pogba scored two goals and two assists in his opening three top-flight outings.
DeAndre Yedlin and Paul Dummett are likely to start as the two wingbacks. I've never had a single problem with him.
"We are second, so our position is better than all the others that are behind us, but there is still a lot of matches still to play and we have to fight for the position". "And it is hard to find a midfield player with more potential than Paul has". Then with so many opinions, and we are in a world of opinions, people can get confused.
"Between me and Paul there are no confusions - he is a midfield player and that's it".
The visitors began to get a grip on possession but their attacking play lacked any real inspiration in the first half-hour, with Jesse Lingard producing their first shot on target 32 minutes in.
Speaking earlier this week, Mourinho insisted that Pogba doesn't need a label - he's simply a midfielder.
Mourinho appeared to question Wayne Rooney's assessment of where Pogba can best operate.
However, Ritchie's 65th-minute victor came against the run of play and the Magpies had to defend for their lives as time ran down.
"I had a few laughs over the past week". Mourinho's men seem to be doing enough to grind out results and I think they'll go away with another three points on Sunday afternoon.
He said: "It was really a great game against a very good team, as top side which everybody knows how good they are".
'It's true. I think it's the only stadium in the Premier League (I have not won at) - also Huddersfield but I played there only once. He can do a bit of everything really well.
However, Jose Mourinho did confirm that the Swedish is back in training, and could return to action quite soon, although it does not seem likely that it will be in this game. The left-back's deal expires in the summer.