Kagawa summed up his feelings in a Japanese TV interview shortly after linking up with his team-mates for the latest leg of their five-match pre-season tour.
"It was a tough time for me with a lot going on in my head. I am not happy with my performance for the team at all," he said.
"I didn't score that much and I also had my injury.
"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."