Easy? I don't think so, after losing some of their core players to injuries it's clear that this has had a big impact and it shows because they're really struggling to score goals in the games they play.
In the last 2 matches in La Liga they did manage to win, but this does not cover the fact that they are struggling and that is evidenced by they only scored narrow wins against clubs that are far below them.
I think what you are saying is very clear to Barcelona who at this moment are fighting very hard to score more goals in every game. One example is in their own home game against Celta Vigo where Barcelona alone were only able to score one goal. Another example is the match in the Champions League group where the result was a draw against Inter Milan, even though it was also a home game for Barcelona, but still unable to take full points and ended in a draw.
This is clearly a problem even though many people say that the injuries of some players do not make them waver but the fact is that at this time they are feeling the effects of losing some players who are still recovering.
Now it's just a matter of seeing whether Lewandowski is still able to consistently score goals or not, because the thought of the Champions League still haunts him.