Rafael Benitez: We have no idea when John Terry will be fit again

John Terry's slow recuperation from a knee injury means he is unlikely to play any part in the Christmas football calendar.

The Chelsea captain has not played since hyper-extending his right knee against Liverpool on 11 November. The prognosis was for an absence of "weeks not months" but he has not played since, and Chelsea's interim manager, Rafael Benitez, said yesterday that it was "one step forward, one step back" with Terry.

The defender has not yet returned to full training and is still limited to basic warm-ups. "He was running on the pitch today," Benitez explained. "Not training with the ball, just warm-up. We have been pushing with doctors. He went on to the pitch and started to warm-up and did some good movement. Then he went with the physio.

"The problem is that he has an inflammation. The knee is so complicated. Sometimes it goes well – today was fine in warm-up but the day after sometimes he has a problem. Hopefully it will be easier in the next few weeks."

Benitez could not predict when Terry would return to full training but the chances of his doing so in time to play over the next fortnight must be slim. "It's positive news [today] but I can't predict when he will be available. I can't guarantee anything."

Injury and suspension have restricted Terry to just 10 starts in Chelsea's 29 matches this season but Benitez insisted the captain's mood was holding up. "He's okay. I saw him yesterday with his family. He was fine, talking and joking. He is just trying to be fit as soon as possible. It's a question of time."

Terry is 32 years old and in the penultimate year of his Chelsea contract. The club's position is only to offer one-year extensions to players in their thirties.

Terry's absence might have meant more responsibility for David Luiz but the Brazilian has been played in midfield recently, where Chelsea are desperately low on numbers.

Benitez said that once Luiz has adjusted to the physical demands, it might be a more natural role for him, as he could express himself while worrying less about the damage done by mistakes.

"It's easier for him [in midfield]," Benitez said. "At centre-back one mistake everyone sees. In midfield it's easier. He likes to play and enjoys keeping the ball, passing the ball and going forward. There it's easier for him than at centre-back.

"It's an option. I played him as a midfielder and didn't want to do it again because it would've been too demanding for him because he's a centre-back. We thought he would not have the same fresh legs. When we have more bodies and options at centre-back it will be easier to use Luiz in midfield. It depends on the game. He can do both really well. He understands the game, is very competitive with good mentality."

Benitez would seemingly rather change Luiz's position than change his nature. He is keen for Luiz to be as expressive and imaginative as he has been. "I encourage him to try things. I would be really worried if a player was not trying things in the final third.

"He's a player who likes to play and wants to help and win. He likes to be seen, to take a risk where it's necessary. So he is encouraged to try things. To do the easy things as well, but there are times he has to try things."

Chelsea play Aston Villa tomorrow. With Ramires returning from suspension Luiz may not be needed in midfield, so he could move back into defence and partner Gary Cahill, himself returning from a ban.