Kagawa joined United from Borussia Dortmund this summer.
He told manutd.com: "Every single day is important. I have to achieve results in each game. That's how I feel. If I play well in one game but not in the next game, I get a poor rating. I want to grow as a football player who can help my team by doing my best everyday, for a whole season. To achieve that, I think it is most important to play in the matches."