The former Liverpool player is not convinced of the France midfielder's worth and believes Jose Mourinho has no excuse for this season's failings
Pogba misses Southampton game
Pogba returned to Old Trafford in the summer following a successful four-year stint at Italian champions Juventus and initially struggled to live up to the expectations born from the staggering price tag.
The France international has impressed in spells under Jose Mourinho this season but has had his overall impact has been questioned by many.
Pogba has made 49 appearances across all competitions for United this season, scoring seven goals and creating four assists, but former Liverpool ace Souness is yet to be convinced by his worth.
"United have to pay a premium. For United, stick 25 per cent on the price," Souness told Sky Sports.
"Because it's Man United and they have the money. In my opinion, they had their trousers taken down paying £100 million.
"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."
Souness' comments came after United's draw with Southampton on Wednesday, the club's sixth 0-0 in 62 outings under Mourinho.
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The Portuguese has pointed blame towards the sheer number of fixtures the club have played this season, however Souness believes the Red Devils are looking for excuses.
"Man up," Souness added. "I'm sorry. These guys have got to perform. Nobody tried to pussyfoot around us. You're no good if you lose next week, deal with it."