Pogba was directly involved in all three of United's goals, scoring twice and setting up Anthony Martial's strike, as they won 3-0 .
Souness, who has repeatedly criticised Pogba during the France international's time at Old Trafford, was again scathing in his assessment of Pogba, despite his excellent display in Europe's premier club competition.
Asked about the France international's performance, Souness told Virgin Media Sport : "If he wants to become a star, someone that can run games and someone people talk about like a proper player, he has to show consistency and leadership.
"He has the armband now and he has got to change his attitude – to football.
"I bet he is a really nice guy but I wonder if he treats football as a bit of a joke.
"I wonder if he trains properly every day, that is a stab at the dark at something that could improve. I don't see him having improved at all since the day he arrived.
"He came in for €100 million and you factor in that Man United do pay a premium because they're one of the biggest and richest football clubs in the world, and the riches of the Premier League, but I don't see much difference in him from when he turned up."
United are next in action against Wolves at Old Trafford on Saturday as Jose Mourinho's side go in search of a fourth successive victory.