Sergio Ramos has been able to complete today's training session with the rest of the squad, meaning that he could be available for Tuesday's Champions League match against Malmö. However, it could be risky to play him in such meaningless game given that Real Madrid already secured a spot in the next round of the European competition, so Benítez most likely wants Ramos to be ready for the meeting against Villarreal.
Ramos has been dealing with a shoulder injury ever since the season started and while he's been able to play in the most important matches Real have faced so far, he has not been the same player he was. Knowing how tricky his injury is, it seems extremely important to make sure he's 100% ready to go before giving him minutes again.
Either way, Ramos is a tough competitor and he will likely be ready for the away game in Villarreal.