Japan attacker has only been a bit-part player in the north west this campaign.
Borussia Dortmund head coach Jurgen Klopp says he had a tearful embrace with Shinji Kagawa before the Japanese midfielder joined Man United last summer.
The German also also slammed the Premier League champions for the way that they have utilised midfield player Kagawa in his debut season at Old Trafford, reports the Daily Mirror.
The playmaker only arrived in the north west in June from the then Bundesliga champions Dortmund on a four-year deal worth £17m.
However, in his first campaign with the Red Devils, the 24-year-old has made just 20 Premier League appearances for the top-flight giants, while overall this season Kagawa has featured in only 26 matches as Sir Alex Ferguson’s side marched to a record-breaking 20th title.
And now his former head coach in the Ruhr Valley has expressed his utter dismay at the way in which the creative attacker has been handled by Ferguson and Co, despite the fact that the Japan star has still managed to find the back of the net on six occasions for United this season.
“Shinji Kagawa is one of the best players in the world and he now plays 20 minutes at Manchester United, on the left wing,” said Klopp.
“My heart breaks. Really, I have tears in my eyes. Central midfield is Shinji’s best role.
“He’s an offensive midfielder with one of the best noses for goal I ever saw. But for most Japanese people it means more to play for Man United than Dortmund.
“We cried for 20 minutes in each others’ arms when he left. One year before that Nuri Sahin went because Real Madrid is the biggest club in the world. If players are patient enough, we can develop the team into one of the biggest in the world.”