Midfielder Shinji Kagawa says he is fighting for his Manchester United future under new boss David Moyes.
Kagawa, 24, played 20 times in United's title winning campaign last season after signing from Borussia Dortmund in June 2012 for an initial £12m.
But the Japan international has played only one league game this season.
"I have to take this like some kind of message [from the manager]. I need to improve more and more, or I cannot survive at this club," said Kagawa.
Moyes replaced Sir Alex Ferguson as United boss during the summer.
Kagawa's only league appearance since the Scot's arrival was against West Bromwich Albion last Saturday, and he was replaced at half-time during the 2-1 home defeat.
That result left Moyes's side 12th in the Premier League table with seven points from a possible 18 and Kagawa admits the substitution has left him in little doubt about the challenge facing him at United.
"I have to take this in a positive way and keep trying to do my best," he said.
"I thought that I would have been able to find some space to create the chances in the second half [against West Brom] - in that sense I was disappointed.
"Sure, I wasn't involved that much. I didn't touch the ball enough, but I was trying to be patient so I didn't feel that bad."