Pogba returned to Manchester United from Juventus last summer in a world record move, four years after he left Old Trafford for the Italian champions.
The 25-year-old has been on the receiving end of plenty of criticism this season with the Red Devils assured of a sixth-placed finish this season.
And former Liverpool boss Souness has been the latest to weigh in.
“United have to pay a premium,” he said on Sky Sports while cover the Red Devils’ 0-0 draw with Southampton. “For United, stick 25 per cent on the price.
“Because it’s Man United and they have the money. In my opinion, they had their trousers taken down paying £100million.
“I’m yet to be convinced by that. He may be a player one day but right now as we sit here after one year in our football, I’m still waiting to be convinced.”
Pogba missed the St Mary’s blank following the death of his father.
The France international was not the only Manchester United player to be at the receiving end of the Scotsman’s ire, as he took aim at Pogba’s replacement in the centre of midfield.
“We’ve got Axel Tuanzebe and Fellaini as the maestros in midfield,” he continued.
“This is Manchester United we are talking about. Man United.
“One of the biggest football clubs in the world, richest clubs in the world and they’re playing those two in midfield.
“They’re looking for them to be creative.
“One is a centre-half and the other one, I’m not quite sure what Fellaini is.”
Jose Mourinho’s side host Crystal Palace in their final game of the Premier League season on Sunday before the Europa League final against Ajax on May 24.