Lampard comes off contract in June.
"You could see the other day he was fully committed and he's a great player, so I will try to bring the best from him in every game," said Benitez.
"At the moment I can see him working very hard in training sessions and games, he wanted to play from the beginning of the first game (in Japan), he wasn't happy but that's normal.
"He's an important player with quality and experience. If he plays well, scores goals and the team is winning it will be easier for everyone to be happy."