Pogba is set to feature in his first Champions League final when Juventus take on Barcelona in Saturday’s European climax in Berlin.
Pogba failed to become part of Sir Alex Ferguson’s plans at Old Trafford and eventually left to join Juventus in 2012.
The 22-year-old has become one of the most coveted talents in European football, and Ballack told Sky Sports he thinks United will regret allowing him to leave.
“It seems like it was a mistake from Manchester [United] to let him go,” Ballack said.
“He has this desire. His physical ability is there. He also has the nous to read situations, and to be in the box to score goals.
“He can still improve that, and if he does he can be an outstanding player.”
Both finalists are going for the treble after securing their respective league and domestic cup titles, with Barcelona the overwhelming favourites to take victory in Berlin on Saturday evening.
But Ballack – who reached the Champions League final with both Bayer Leverkusen and Chelsea – believes the result is not a foregone conclusion.
“Barcelona will pay a lot of attention to themselves, to make their own game so that it runs with offensive, attacking football – with Messi, Neymar and Suarez up front,” he said.
“Juventus is a really strong opponent. They’re like Italian teams usually are. Tactically very well educated.
“So it’s not like Barcelona are the better side, they are the big favourites and they will win it. I think it’s quite even.”
Watch live coverage of the Champions League final, Juventus v Barcelona, from 6pm on Sky Sports 1 HD & 5 HD.