Benitez, who helped Torres become one of the best strikers in the world at Liverpool, acknowledged the 28-year-old was not the same player he had been before joining Chelsea.
But he insisted the striker could still make himself an asset rather than a liability at Stamford Bridge, and to do so, he needed to get down the gym.
"We have to improve some players physically and they will come back to maybe the strength they had," Benitez said, insisting age or injuries had nothing to do with Torres's loss of explosive pace.
"He has to train in a way that suits him. We will try to find this way.
"It's a question of time, but we know we have to change the movements we're working. You have to work in the gym on strength. Maybe he needs to do that again."
Three Blues managers have failed to get Torres scoring regularly, each repeatedly insisting there was nothing wrong with the forward.
But the man who knows his fellow Spaniard better than any of them said: "He's not exactly the same player now, because he was at maximum level at this time (at Liverpool). But I think he can come back. How close? I don't know. It depends on the rest of the team. I'm sure he can improve, but the team has to help him."
Torres also has to help himself, as does Benitez, following a run of just 19 goals in 88 games for the European champions.
"The first thing is to give him some confidence, instructions as to how he can do things in a different way, improve him a little bit physically," said Benitez, who wants Torres's team-mates to create more chances for the striker and win the ball back faster.