Alexis Sanchez was unable to "connect emotionally" with his Manchester United team-mates following his move according to his former Chile coach.
The forward swapped Arsenal for United in January 2018 in a deal that made him the Premier League's highest paid player.
But a return of just five goals in 45 outings means the transfer has failed to live up to expectations.
Sanchez has since been shipped out to Inter Milan in an effort to rediscover the form he showed across four years at Arsenal.
But Juan Antonio Pizzi, who led Chile to Copa America success in 2016, reckons the 31-year-old's drop off stemmed from a lack of emotion.
“Alexis was in a perfect place at Arsenal,” Pizzi told the Guardian.
“Suddenly he changes city, coach, teammates, fans [by joining Manchester United ] ... sometimes that adaptation happens quickly, sometimes it takes longer.
"In Alexis’s case, I think it took too long. He didn’t seem to be able to connect and emotionally he dropped. The consequences of that state of mind were translated in his performances.
"I don’t know what destiny holds for him but I think this experience in Italy [at Internazionale], away from English football, might be good for him. I really hope so. I’m sure that if he can find tranquillity and his form, he’ll be very important for United.”
In Serie A Sanchez has started in just two of his 15 appearances, scoring once.
Nevertheless, United boss Ole Gunnar Solskjaer has backed the Chilean to "prove everyone wrong" once he returns to Manchester.
"Alexis will come back in the summer and prove you all wrong," claimed the Norwegian earlier this year.
His task could be made all the more harder though should the club secure some of their summer targets such as Jadon Sancho.
