With Ilkay Gundogan, Pedri, Gavi, Ronald Araujo and Frenkie De Jong all out, new manager Hansi Flick gave 20-year-old academy midfielder Marc Casado his senior debut, playing alongside three 17-year-olds in Lamine Yamal, Pau Cubarsi and Marc Bernal.
Nevertheless, Barca showed enough strength to fight back and win thanks to a Lewandowski brace.
"It was very important to start with a win in such a difficult stadium and with the problems we faced," Lewandowski told Movistar Plus.
"We didn't play well for the first 20 to 25 minutes. In the first half we had problems to get close to their box but then we started playing much better and we did it with three or four very young players.
"If you can win like this with such young players it is something special and they have shown a big potential. No signs of the lack of experience, they played very well with possession and without the ball. We could have won by a larger margin, but it's great to start the season with a win."
