Borussia Dortmund were knocked out of the Champions League after losing 3-1 to Monaco in a quarterfinal second leg on Wednesday.
Shinji Kagawa played the entire 90 minutes as Dortmund were beaten 6-3 on aggregate. With Leicester City's Shinji Okazaki going out the day before, Kagawa was the last Japanese remaining in the competition.
Kagawa was trying to reach the semifinals for the first time.
"To get to the next round, I need to take it up another notch, technically as well as physically," the Japan midfielder said. "I didn't think we would win 2-0. I thought we would need at least three goals."
"Even from the last 16 to the quarterfinals is a big jump in terms of the individual quality on the pitch."
Dortmund fell behind early, with Monaco's 18-year-old France striker Kylian Mbappe netting in the third minute before Radamel Falcao made it 2-0 in the 17th.
Marco Reus pulled one back for the visitors shortly after halftime, but Dortmund's heads went down nine minutes to time when Valere Germain struck Monaco's third.
Kagawa tried to put a positive spin on the defeat despite a draining week for Dortmund, who were ordered by UEFA to play on following the bomb attack on the team bus ahead of the first leg.
"Not everything is bad about this. We now know that some of what we do works at this level. We can definitely compete on this stage," he said.