OSAKA, Japan - Japan Shinji Kagawa's finally broke out of his long sulk on Wednesday after helping crush Tajikistan 8-0 in a World Cup qualifier the previous evening.

The Borussia Dortmund midfielder scored twice, both absolute stunners, in Osaka, and told reporters: "Now I have to keep producing the same results."

Kagawa spent much of his time in his hotel room before Tuesday's game after a crisis in confidence, triggered by a foot injury in helping Japan win the Asian Cup in January.

His Japan team mates refused to wrap him in cotton wool, however, and Kagawa responded with two superb goals, albeit in an embarrassingly one-sided World Cup qualifier.

The 22-year-old insisted he had turned the corner after shaking off a worrying slump in form to help Japan to the top of Group C on goal difference from Uzbekistan.

"It's given me a lift for sure," he told reporters. "Mentally it's a relief and I can go back to Germany on a positive note."

Kagawa was anonymous during Japan's late 1-0 victory over North Korea and 1-1 draw in Uzbekistan in their first two group games.

If Kagawa's first goal on Tuesday -- a cheeky flick with the outside of his right boot -- was good, his second would not have looked out of place at any of the world's great arenas.

Spotting the Tajik goalkeeper on the edge of his six yard box, Kagawa shaped to cross before smashing home a viciously dipping right-foot shot from the edge of the box.

"I went for it," he snapped when asked if he had meant to shoot. "The games get tougher from here and I hope I can get in amongst the goals quicker."

Recently left on the bench by his Bundesliga club for the first time, Kagawa's performance repaid Japan coach Alberto Zaccheroni's faith in him.

"We all know how dangerous and important a player Shinji is," said the Italian. "He played fantastic. He scored but more importantly other players stepped up too."