I'm yet to see the best of Lewandowski in Barcelona, he's not played up to the standard he did at Bayern Munich that made Barcelona bring him into their Squad, this is a player that was known for scoring numerous goals in a single season, getting hat-tricks in several matches but at Barcelona he's not scored like that even with enough chances created for him.
He has a lot of good quality players built around him so I expect alot from a player of such calibre to deliver his team against lesser clubs, well thanks to his penalty goal that made them win Osasuna and I believe the goal he scored would increase his morale to perform better in their next match and start scoring more goals as expected by him, if Lewandowski fails to improve before the winter window it would leave Xavi with no option but to seek another alternative in that position.
Could it be that he was already starting to experience a drop in performance? because he's 35 years old, or maybe because he doesn't get enough ball support from the Barcelona midfielders like he did at Bayern Munich? because when he was at Bayern Munich he was a very productive striker.
However, I think this is only due to the decline in the performance of the whole team so that he looks unproductive, but Barcelona will depend on him to score goals.
In 4 matches Barcelona have actually never won very convincingly, they looked weak in defense so they conceded 3 goals to Villareal and Osasuna who managed to score 1 goal against them.
Joao Felix is already in the Barcelona squad, but will he be a productive second striker so that Barcelona can play well again and win convincingly? this is still a question.