Despite this, Lewandowski did not appear to be the best rated player of the game but he was the worst rated player based on the aiscore. Kounde and De Jong were the two players who had the highest ratings in that match, but I agree that overall Barcelona didn't perform as good as expected in that match.
Lewandowksi isn't good like his was, I think his performance is declining in this season. If Joao Felix can show a good performance, I believe Barcelona will sign him to replace Lewandowski's position.
Joao Felix is not to replace Lewandowski, but Felix is expected to be able to make an impact on the left wing even though his main position is second striker. Joao Felix still needs to adapt to Barcelona's game scheme this season even though he is already quite experienced in La Liga. While Lewandowski has basically tried his best to contribute to the game, he admits that the strategy Xavi has implemented in recent matches has made it difficult for him to perform like last season.
In the last few matches, Xavi has given full trust to Lamine Yamal, making it a little difficult for Lewandowski to get the ball. Lamine Yamal can perform well, but sometimes he is not good at serving the main striker even though he can send accurate passes to other players. Lewandowski complains about this, but I believe he must keep trying as much as possible and still have to maintain his performance even if Xavi slightly changes his game strategy.
Osasuna is really good in counter attack, they can maximize their chance to score a goal. While Barcelona only keep passing in order to make them looks more dominant and giving pressure to Osasuna.
That's normal for any team, especially when they play against dominant teams like Barcelona or Real Madrid. Their strategy has not changed, meaning they just try to defend as best as possible and counterattack and take advantage of opportunities. In some games this strategy works, but other times they fail.