I think Barcelona still should make two transfers to specific areas. These areas are defensive midfield and centre-forward. Because in the defensive midfield there is still only Oriol Romeu. Of course players like de Jong and Kessie can also play there. However their main positions are central midfield so it is better to use them there.
Agree. Those 2 positions have no proper substitution players, even I don't think Oriol Romeu will be strong enough for defensive midfielder. Barcelona ideally must bring a stronger player in the position, but Barcelona has the problem with their financial. It makes them difficult to buy new players in the current transfer window.
For the other position there is only Lewandowski there. Barcelona don't need to spend so much money for bringing a striker. They can even loan someone who can be useful in Lewandowski's absence. Signing a backup striker should be even the priority for them.
They may expect Lewandowski can always be in his good condition. We know he rarely got injury, he has a good fitness. But I agree that it is not impossible for him to get injury during the whole season. Sure, Barcelona should get a loan for a striker at least, it is the best option that they can do. There are many strikers who want to play with Barcelona.