The Japanese international joined the Red Devils from Dortmund in 2012 for around £12 million, and having shown glimpses of his best form in his first season, appears to have gone backwards under David Moyes.
Kagawa has made just nine league starts for Manchester United this season and is yet to score - although he did start in the 4-1 win over Aston Villa at Old Trafford yesterday, teeing up Wayne Rooney for the home side's first goal of the match.
Dortmund boss Jurgen Klopp admitted in an interview last year that he was 'heart broken' to see Kagawa struggle at Old Trafford - but could now offer him a route back to Germany in the summer.
The Mirror report that the 2013 Champions League finalists are interested in ending his old Trafford nightmare by taking Kagawa back on loan for next season.
Kagawa's chances of first team action in his favoured central position have been further limited by the arrival of Juan Mata from Chelsea in January, while Moyes appears to favour deploying Rooney just off the striker.
The 25-year-old may fall further down the pecking order if reports of a £200 million Manchester United spending spree is to be believed.
Moyes is set to be handed a transfer warchest to revive the Red Devils, with Bayern Munich's Toni Kroos said to be high up the Scot's hitlist.
Borussia Dortmund meanwhile warmed up for their Champions League quarter-final against Real Madrid with an impressive 3-2 comeback win against Stuttgart yesterday.