Old Trafford staff are concerned about the injury sustained by the Japanese star on international duty as they also sweat over the fitness of Robin van Persie ahead of Wigan clash

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By Wayne Veysey | Chief Correspondent Manchester United have sent Shinji Kagawa for scans on his back to determine the extent of the injury he picked up on international duty,can reveal.Sources have said that the Japanese star returned to United’s Carrington training base still feeling discomfort in his back following a 12-hour flight from Japan to England on Wednesday.The club’s medical staff are now taking steps to get to the bottom of the intermittent back problems suffered by Kagawa since starting his professional career.The 23-year-old is regarded as a major doubt for Saturday’s home clash against Wigan Athletic as he undergoes further assessment.The fresh blow to Sir Alex Ferguson’s plans comes as Robin van Persie is also unlikely to be risked at the weekend after being subbed at half-time in Holland’s win over Hungary on Tuesday with a thigh problem.It is understood that the Dutchman will undergo a 48-hour assessment as United adopt a safety-first policy because of his chequered fitness record.Ferguson’s new injury dilemma comes as he prepares the team for Saturday and the return of the Champions League group stages next week without Wayne Rooney, Ashley Young and long-term absentees Phil Jones and Chris Smalling.Javier Hernandez, who has been moved down the striker pecking order following Van Persie's arrival, will come into contention for a starting spot against Wigan, with Danny Welbeck almost certain to lead the line.United are particularly wary of Kagawa’s back problem in light of his past fitness issues.The attacking midfielder felt a twinge during training, and despite treatment, he was eventually withdrawn from Japan’s team shortly before kick-off against Iraq in Saitama, a game they went on to win.Speaking on Wednesday before boarding a flight back to England, Kagawa said the problem was “not serious” and added: “I think I can come back [to play] soon. I have to consult my medical staff and do my best until the next match.“It may be due to travel and fatigue. I can get by if I take good care of my body. I’ve learned a good lesson from this.”The lightweight 5ft 7in midfielder, who has started all three of United’s league fixtures following his summer move from Borussia Dortmund, added: “After moving to the Premier League, I’ve realised that I need to limber up and strengthen my body trunk.“Tough games are going to start and I will have to fight for a regular spot. I want to go out in perfect condition.”