The 24-year-old played alongside Pogba in the reserves at Man United for three years before the Frenchman left for Italy in 2012.
He has returned to Old Trafford in a world record deal worth £89 million and is rated as one of the best midfielders in the world.
Speaking about Man United, King claims Mourinho has made four great signings this window.
“United have made four great signings,” he said.
“I played with Paul Pogba when I was there and he is an amazing player. He has been like that since day one and always had the talent.
“They have also got Ibrahimovic and he has won titles everywhere he has been. United have had a good transfer window so far.”
“Pogba is one of the best midfielders, if not the best, in the world right now and he is only 23. He is only going to improve and playing under Mourinho is just going to make him better.
“I always saw the potential in him and was a bit surprised when he left for Juventus. But that’s football and it doesn’t always work out. Not many players have left United and come back.
“I’m very happy for him that he’s doing so well. He has set the record transfer fee which is amazing. United have got an amazing player back and I think he will do well. He is worth every penny.”
Pogba’s deal is an exceptional capture for Man United and it sends out a message of Jose Mourinho‘s intent to build a squad capable of winning titles.
Pogba is one of the best midfielders in the world, as King suggests, but the Frenchman is only 23 and will improve as he picks up more experience at Old Trafford.