Shinji Kagawa has stated that David Moyes should be asked why he has not yet played him in a competitive match for Manchester United this season, with the midfielder admitting to being frustrated by his lack of opportunities.

Since Moyes became the United manager in the summer, Kagawa has managed only seven minutes of football, as a late replacement in the 2-0 Community Shield win over Wigan.

Moyes has said that the 24-year-old was initially returning to match fitness and then decided Nani was preferable as a substitute for the 1-0 defeat at Liverpool before the international break. The playmaker then equalised for Japan in Tuesday's 3-1 win over Ghana in Yokohama.

"Please ask David Moyes why I'm not in the side," Kagawa told AFP. "It is frustrating not playing but to score a goal like that gives me confidence. Hopefully I can take that back to my club with me and things will improve. It's hard not playing regularly. Some days the frustration is worse than others – it comes in waves.

"So it's nice to come back to Japan and get to play, and to score felt good. I just have to keep working hard and keep pushing for my chance. When I get back it will be a challenge to get into the team.

"When I get back to my club I have to wait for my chance in the Champions League and the Premier League. I'm sure my chance will come."

On Saturday United host Crystal Palace before Tuesday's Champions League group game with Bayer Leverkusen. Moyes's side then make the trip to Manchester City on 22 September for the derby, where there will be heightened security.

Greater Manchester Police are concerned there will be no repeat of the trouble that blighted the corresponding fixture last December, which United won 3-2. Rio Ferdinand was hit by a coin and one supporter managed to get on to the pitch.

GMP officers are expected to be on the lookout for graffiti – there have previously been messages regarding the Munich air disaster and the death of the former City midfielder Marc-Vivien Foé – and sniffer dogs will be used to locate flares.