Injury may rob Shinji Kagawa of a Manchester United Champions League debut.

Kagawa has handed Manchester United another injury headache after sitting out Japan's World Cup qualifier with Iraq with back pain.

The midfielder suffered the knock in training on Monday and was ruled out of his country's match just an hour before kick-off.

Kagawa is now a doubt for United's clash with Wigan on Saturday and their Champions League opener against Galatasaray next Wednesday.