Barcelona striker Robert Lewandowski hopes Tuesday's 3-1 defeat to Borussia Dortmund in the Champions League will serve as a wake-up call after a frustrating night in Germany.
Serhou Guirassy struck a hat trick for Dortmund to end Barça's 24-game unbeaten streak in all competitions, but the Catalan side progressed to the semifinal 5-3 on aggregate after a 4-0 first leg victory last week.
Lewandowski, who was whistled by the home supporters throughout the game on his return to the club he played for between 2010 and 2014 before joining rivals Bayern Munich, was critical of Barça's display.
"We lacked control in midfield and we made a lot of mistakes," the Poland international told reporters. "We lost possession, gifted them the ball... We made it easy for them to create chances.
"We need to properly analyze the game. We have to learn from it. We can't play like we did. If we have to lose and make mistakes, it's better that it happened now. In the future there will not be room for so many errors.
"We congratulate Dortmund for their performance. Maybe it's the wake up call we needed. We have to learn from this."
Lewandowski scored twice in the first leg at the Olympic Stadium to give Barça a four-goal advantage heading to Signal Iduna Park on Tuesday.
Three goals from Guirassy, the competition's top scorer with 13, had Dortmund believing a comeback was possible heading into the final stages, but the Bundesliga side never got within one goal of Barça on the night in the end.
"It was a crazy game," Lewandowski added.
"Looking back at the two games, we're in the semifinals because we deserved it, but there was some tension and anxiety out there tonight."
Barça coach Hansi Flick said he had to remind his players they had reached a first Champions League semifinal since 2019 such was the disappointment in the dressing room after the game.
The defeat capped a run of seven games in 20 days since the March international break, which Barça have emerged from alive in all three competitions still.
They now have back-to-back LaLiga games at home to Celta Vigo and Mallorca as they look to maintain their four-point lead at the top of the table, with the Copa del Rey final against Real Madrid following on April 26.
Either Inter Milan or Bayern will then await them in the last four of the Champions League.