Great, Atletico can beat Bilbao in the middle of the schedule with a fairly difficult opponent. Because in the next match Atletico will also play away against Real Madrid at the Santiago Bernabéu, obviously it will not be an easy opponent.
Because Atletico must also be able to maintain their position in the top four, because Atletico's current position is still not completely secure there and Atletico still need to win in every match.
Since the only competition that Atletico is still playing is La Liga, I think they do have a little chance against Real Madrid in the away game. Real Madrid might need to rotate a little bit and not send their best eleven players into the game. Then again if Real Madrid wants to preserve a little chance for the championship they are actually forced to win that game. If Barcelona can extend their lead by another three points, I just can't see how in the world Real Madrid could make a comeback. It is a tricky situation for Real and Atletico can just give their very best and don't have to care about recovery times or injuries. That's a totally different situation for Real.
For a derby match like this I think Real Madrid will still play all the main players, and it's not about getting the La Liga title or not. Because in a derby match like this, of course they have high prestige, so they must win.
Even though Real Madrid also has a schedule with difficult opponents because Real Madrid has to play in the Champions League against Liverpool and also in the Copa del Rey against Barcelona, but I'm sure that this will not make Real Madrid weak when playing against Atletico.