Shinji Kagawa has quashed claims he is not fit enough to play for Manchester United after playing 85 minutes for Japan on Tuesday, claiming he does not know why he isn't being picked at Old Trafford.

The Japan international has been overlooked by United boss David Moyes during his side's opening three Premier League games of the season, with his only participation coming in a brief cameo appearance in a Community Shield win over Wigan Athletic that lasted just seven minutes.

Despite Moyes stating after United's last game the former Borussia Dortmund playmaker is still looking for full match fitness, Kagawa seems to have no such problems when representing his country after netting a fine equaliser which sparked a comeback as Japan defeated Ghana 3-1 in Yokohama.

"Please ask David Moyes why I'm not in the side," Kagawa told AFP after his nation's win on Tuesday.

"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. "

The Japanese international was an unused substitute in United's first two games of the season and was left out of the squad completely in their recent loss to arch rivals Liverpool, a decision that provoked the ire of some supporters given United's dearth of creativity in that game.

Still to see any Premier League action this season, Kagawa admits a return to his international fold has been a welcomed break as he struggles to find a way back into Moyes' first team plans.

"It's hard not playing regularly. Some days the frustration is worth 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 missed one in the first half tonight so when the chance opened up in the second for me to shoot I wanted to take it on."

After winning a Bundesliga and German Cup double with Dortmund, the talented playmaker made his move to Manchester last summer but endured a mixed first campaign during his first season in English football.

A knee injury that side lined him for four months derailed his first half of the season and the playmaker would drift in an out of Sir Alex Ferguson's first team plans for the remainder of the campaign. But the Japanese star provided glimpses of his undoubted talent, chiefly in his hat trick performance against Norwich City in March.

Kagawa's agent revealed his client did receive an offer from Atletico Madrid during the summer transfer window, however the playmaker insisted he had no intention of leaving Old Trafford.