He started Wednesday's 2-0 FA Cup win at Middlesbrough - but he is not guaranteed to play every week.
Benitez said: "He went 16 weeks without training and he's missed some training with a problem with his knee. But if he can complete a normal training session with his knee, he can play more.
"He was training today. If he completes more sessions, he will be fine. He wasn't playing too much, but now he's playing more minutes and, if he continues training, he'll have more.
"He was missing two or three sessions. We had a specific plan created for him, and he couldn't complete two or three sessions. It was taking too long. We had to prepare a proper plan and be sure we had all the steps in place.
"He was really pleased with the plan and was progressing. Thanks to this plan, and the job of the fitness coaches and the medical staff, he can carry on training and normally play games. But before it was quite difficult. He's an important player for us.
"He has quality, he is the captain. I must know whether he can play two games a week with the intensity."