Benitez says he will be aiming to utilise both players for the remainder of the season.
"When I arrived we had Terry and Lampard injured. Now, Lampard is playing and Terry is coming back. It's good to have different options, but it's still early because to gain match fitness Terry has to play, but you cannot play him in this type of game as he will have to play high, and that's more difficult if he's not fit," he said.
"I can understand that Frank, from day one, has been doing a great job. He is under contract, his commitment is there and I'm really pleased with him.
"Every player here has to compete for his position. That's good for the team, and also for me as a manager because I can make decisions. If you have two or three options it's easier to manage."