Just like Real Madrid, which is most likely targeting victory against Real Betis, but it might not be easy because Real Betis has also improved recently, and Betis also has the advantage of playing at home.
If you look at the schedule, Real Madrid will have to compete against Atletico in the Champions League in the next 3 days, so there is a possibility that Real Madrid will not play some of their key players for the full 90 minutes in the match against Betis, and it could affect their performance.
Yeah it's looking more like it after a penalty in Tonights game, goals conceded already and now Realmadrid need atleast 2 goals maybe to win the match provided betis doesn't score another goal before them.. a draw isn't that okay in this kind of time for Realmadrid and draw or loss will give advantage to both or one of either Barca or Athletico Madrid.
About not playing their full squad till end, I don't think they have much choice especially now that they are one goal behind unless they want to give up the victory. Besides, both Real and ATM will be somehow faced with same challenge in the upcoming UCL game, don't forget ATM already played Barca and they barely had enough rest before play Bilbao tonight.