Manchester United midfielder Shinji Kagawa says he is unhappy with his form since moving to Old Trafford.
The 23-year-old, who joined United from Borussia Dortmund in the off-season, made an impressive start to life in the English Premier League with two goals in his first six games.
The Japan international has returned to action after being sidelined for 10 weeks with a knee injury and said he needs to contribute more to the team.
"I'm really feeling that I need to perform better," Kagawa told reporters.
"I'm not satisfied with what I have done here at all. It's a big and really famous club in the world and I need to overcome lots of pressures and be mentally stronger.
"Unfortunately I got injured, but I have to be better and grow as a player a person, in terms of contributing to team's wins and succeeding here."
The former Bundesliga Player of the Year has backed himself to improve, insisting he can emulate the mental strength shown by United's established stars to ensure he is not considered an Old Trafford flop.
"I really feel that we have a strong ability to bounce back when we are behind, so people in this team must be really mentally tough," Kagawa said.
"We have a really strong squad with many world class players, so it's lucky for me to have opportunity to train with them and play games with them."
Kagawa also hopes to draw inspiration from Manchester United supporters and manager Sir Alex Ferguson, who he was quick to praise.
"Sir Alex is one of the best managers in the world," he said.
"What I am really impressed [with] are the numbers of great players he has helped to grow, the numbers of titles he has achieved for the team almost every year, and his ability to mould top players into a team.
"Also, the atmosphere supporters make at Old Trafford helps the team to fight back. As I said, my team-mates are so experienced and mentally strong."