The Japan international has found his first-team opportunities limited under new Red Devils boss David Moyes this season, starting seven top-flight games.
I realise the Premier League is a very tough league and I know I have to be stronger
In fact, Kagawa has only racked up 24 Premier League starts since the highly-rated 24-year-old completed a £12m move from Borussia Dortmund in June 2012.
But the United midfielder acknowledged he must become stronger if he wants to survive in the demanding English top-flight.
“I think I can still improve my strength. I’m not the tallest or biggest player, so I have to move my body more,” Kagawa told United’s website.
“Smaller players in the Premier League are very good at using their bodies [to get past the opposition] and that’s what I will continue to do.
“I realise the Premier League is a very tough league and I know I have to be stronger.”
Despite speculation surrounding his Red Devils future, Kagawa insisted that he is enjoying working under Moyes this season.
He added: “It has been quite hard work and training is fairly intense because there have been so many games recently, so we have had to concentrate on practising in a very short period of time. But the sessions have been very good.”
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