Borussia Dortmund midfielder Shinji Kagawa said he is disappointed with his personal output in 2014-15.
The former Manchester United man has scored just five times in 30 appearances in all competitions for Dortmund, who have battled back to a position of relative strength after a shocking start to the Bundesliga season.
The Japan international, who suffered head and groin injuries this term, said it was a negative campaign.
"It was a very difficult season because I wasn't able to play well consistently, neither was the team," the 26-year-old said.
"I have struggled through the season but towards the end of the season we have been able to get some wins.
"So as a team, it's clear we are getting better. Personally, I can't be happy with my performance because I didn't score much."
After previously battling in the relegation zone in Germany, Dortmund are fighting for a spot in next season's UEFA Europa League - as they sit two points behind sixth-placed Schalke with two games to play.
Jurgen Klopp's men can also seal a European place by beating Wolfsburg in the DFB Pokal final on May 30, but a loss would render their current standing in seventh as a Europa League ticket.
First, Dortmund travel to Wolfsburg for a league fixture on Saturday.
"Playing against the same team twice in a short period will be difficult, despite the fact it's two different tournaments," Kagawa said.
"They are two very important matches.
"The boss has said they are different games and firstly we have to prepare well to get the three points on Saturday.
"We are thinking of that now rather than the DFB Pokal final."
On Klopp's imminent departure at season's end, Kagawa said he anticipated a turbulent period - as he suffered a goalless campaign in David Moyes' first season at Old Trafford in 2013-14.
"A new boss is coming, that means it is difficult for me like it was in Manchester," Kagawa said.
"But the most important thing is to trust each other and set the same goals, then go forward in the same direction and work together.
"We have to work hard before the season starts. That's the only thing we can do. We must have the same target and believe in him, I'll do my best."
