The boss is pleased to see his £20m signing settling in now and has predicted Aquilani will have a big part to play as the Reds look to take that final Champions League qualifying spot and win the Europa League.
"It was a shame he was sick because he had been good for the performance [against Portsmouth]. You can see he wants to improve and it is important for us to have another player pushing," said Benitez.
"We need players with quality to help us improve until the end of the season. Alberto has got desire and he is working very hard. When we have him available, he can give us a different approach on the pitch in different games.
"Physically you could see he coped with a lot of running last time and it was much better.
"It is a question of time. It is disappointing that he was ill and missed out against Lille but we are hopeful he will continue to improve and play more games before the end of the season."