Mkhitaryan played under Klopp for two years at Borussia Dortmund having joined the club in 2013 from Shakhtar Donetsk.
Despite not winning any trophies during their brief spell together, the Armenian believes Klopp’s influence off the field has helped him the most.
“I had chosen Dortmund because I liked the way they play there,” Mkhitaryan told German media, according to the Echo.
“The players also liked me – and then there was the great coach, Jurgen Klopp.
“After I had talked to him, the decision had been made for me. I only wanted to go to Dortmund.
“When I came to Dortmund, Jurgen Klopp told me that I had to let go, and that it’s not good to think about football all the time.
“I started to understand what he meant, and so slowly, this part of me has changed.
“I am thankful to Klopp. He worked on my personality and the psychological part.
“Klopp showed me the way. He supported me and told me I had to keep my head up because good things were coming.
“He helped me to become a better player.”
Mkhitaryan will go up against his former manager for just the fourth time when Liverpool host United on Sunday, and the Armenian is still looking for his first win.
Mkhitaryan now showing he is at home in the Premier League
Despite Jose Mourinho signing Mkhitaryan as one of his first actions as United manager, the 28-year-old struggled to make much of an impact at Old Trafford last season.
However, this season the former Dortmund man has been on fire alongside Romelu Lukaku and Marcus Rashford in United’s front three.
Creatively, Mkhitaryan has averaged 3.58 chances created per 90 minutes this season, compared to just 1.87 last season.
The increase in chances created has also seen the Armenian record more assists at an impressive 0.81 per 90. Last season, he made just one assist in his 24 games – an average of 0.07.