Let's see how they recover physically, especially Pedri who has played all the games in the EURO and the whole season with his club. I agree that it might be a problem if they are not at the same level that these days, but even without the 6 players, I think it's possible to make a competitive team.
For example, Marco Asensio, Dani Ceballos or Bryan Gil have already played for the senior team, but this season they haven't played much due to different reasons, so this is a very good opportunity for these 3 guys to show how good they are and convince Luis Enrique to make the senior list in September. And I would also add to this list the name of Rafa Mir, he's quite unknown, even in Spain, since he plays for Huesca, but in my opinion he can be part of the senior team this season considering the low level of Spanish forwards. He plays different compared to Dani Olmo or Mikel Oyarzábal, which is always nice to introduce some tactical variations during the game.
Anyways, I don't like the draw at all. Facing Germany or Brazil (if we get through the group stage) in QF is not going to be easy. Good luck!