Benitez said: "Obviously, we are really pleased that Ryan is coming back to training because he is an important player for us and he has worked hard to recover from the injury he suffered with Holland.
"But we are really worried because after getting him fit again it is likely that we could lose him again if he is selected for the Olympics. This is a big problem - we prepare him and then he goes away with the national team.
"This season is very important for him. In his first season he was settling in but this time he has more experience and we are looking for him to give something from the beginning so it is really important for him to start working with his team."