Shinji Kagawa
Dortmund would be open to re-signing Kagawa in the future. (Reuters)

Borussia Dortmund would welcome Shinji Kagawa back to the club with open arms should he ever leave Manchester United, but do not expect the attacking midfielder to depart Old Trafford any time soon.

The Japan international left the German giants for United last summer where he enjoyed a mixed start to life in the Premier League, where his occasional moments of brilliance were compounded by a troublesome knee injury and a struggle to impose himself on the starting XI.

Kagawa was recently quoted as saying that he would like to one day return to Signal Iduna Park if the club will have him after just one season in the Premier League, leading to Dortmund CEO Hans -Joachim Watzke insisting his club would jump at the chance to re-sign the 24-year-old.

"The door is always open for Shinji," Watzke was quoted as saying by Bild. "A transfer is not an issue at the moment, though."

Kagawa penned a four year contract at Old Trafford upon sealing his £16m move in 2012, and although the creative midfielder appears determined to succeed in Manchester, his agent suggested a move away from the club in the future is not beyond the realms of possibility.

"At the moment, I expect Shinji to stay at Manchester United. However, you never know what will happen in football," Kagawa's agent Thomas Kroth was also quoted as saying by Bild.

Kagawa has often been his biggest critic when looking back upon his first season on England, unsatisfied with the impact he has had at his new club. His return of six goals and three assists in his 20 league appearances would appear to be a respectable haul for a Premier League debutant, but the former Dortmund star has his eye on greater improvement.

After returning from an extended summer break following his participation in the Confederations Cup with Japan, Kagawa has joined up with United for the third leg of their tour of the Far East, although he is not expected to feature in Tuesday's game against Yokohama F Marinos. Having done enough to initially convince Sir Alex Ferguson to bring him to Old Trafford, Kagawa is now eager to swiftly impress his new boss in David Moyes.

"We still need more time to get to know each other, but I am looking forward to building up our relations," Kagawa said yesterday in a press conference.

"As a player, I feel every game is important and I want to give my very best and to give a good impression to the coach."