Manchester United midfielder Shinji Kagawa has revealed he's been unhappy with his contribution this season despite winning his third league title in as many years.
The former-Borussia Dortmund star won back-to-back Bundesliga trophies in Germany before moving to Old Trafford last summer.
But injury problems and a lack of form have led to a stop-start season for the Japanese international at United.
He told ESPN: "I was looking to produce even more results. I was injured and I felt things didn't go well easily.
"I had a lot of conflict, frustration and worries. In that sense, I think it has been a profound year.
"Honestly, I haven't contributed as much as I did at Dortmund. I was even injured. I still don't quite have that feeling of accomplishment. But I've managed to win three in a row.
"I think my career is bound to get better and better."
Kagawa has enjoyed a run in the team in recent weeks, and made a telling contribution against West Ham last week as well as scoring a hat-trick against Norwich City in early March.
Along with the £24m Robin Van Persie, the Japan international was Sir Alex Ferguson's big summer signing at the end of last season.
But while Van Persie has been widely credited as the difference between United and title rivals Manchester City this term, Kagawa has failed to reach such heights.
He's showed promise in recent games though, and will be looking for an injury free campaign next year as United aim to defend their title.