Shinji Kagawa has admitted he was disappointed with his performance level and his goal return in his first season at Manchester United.
The Japan international, who joined United from Borussia Dortmund last summer, scored six times as he helped the club to their 20th Premier League title.
However, Kagawa, who had struck 17 times the previous year at Dortmund, was frustrated by his displays in an injury-hit year
"It was a tough time for me with a lot going on in my head," Kagawa told the Premier League's official website. "I am not happy with my performance for the team at all. I didn't score that much and I also had my [knee] injury.
"Despite that, it was great we won the league, I just don't feel that I achieved everything that I wanted. For me personally, it wasn't a good season."
United boss Sir Alex Ferguson often used Kagawa on the left wing, instead of in his preferred No. 10 position, but the 24-year-old has insisted he must do better, wherever new manager David Moyes chooses to play him.
"I always think that I must play well. And I always have an image in my mind of how I want to play, wherever the position," he said. "Whenever there is a tough time, whenever it gets difficult for me, I just train and look ahead to the future."