The 32-year-old sustained a knee injury against Liverpool in November and has been out of action ever since, missing out on the Blues' ill-fated Club World Cup campaign as a result.
The former England captain is yet to feature under the Spaniard, but Benitez insists he is aware of Terry's importance to his Chelsea side.
Chelsea are 8/1 with Bet365 to beat Aston Villa 3-0
"John Terry is training, doing some running, but he's not available yet," the Blues boss told reporters. "We cannot predict how long it will take.
"Terry is the captain because he is a leader, he can help and push when necessary. All the players are important, but John's the captain and on the pitch he can do well because of his character."
Benitez also revealed Liverpool target Daniel Sturridge is close to a return, but refused to comment on speculation linking him with a move to Anfield in January.
"Daniel Sturridge is also back in training, he trained very well this morning," he continued.
Chelsea return to Premier League action against an Aston Villa side high on confidence, and Benitez says the Villains' qualities mean he is not taking anything for granted.
"Aston Villa are unbeaten in five games, they are comfortable and have good options on the counter-attack," he continued.
"Christian Benteke is a good player, strong in the air and good with the ball."