The Japan international, who moved to the North West outfit from Borussia Dortmund last summer, netted six goals and made 17 Premier League starts, but despite winning the English title, Kagawa believes that he could have done better on a personal level.
"I am not happy with my performance for the team at all," Kagawa told the Premier League's official website. "I didn't score that much and I also had my 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."
Kagawa is currently representing Japan at the Confederations Cup.