It is Gerrard's first match since he was arrested and charged with assault and affray following a brawl at a Southport nightclub in the early hours of Monday.
Benitez said: "Gerrard will play. He is ready and, after we talked it over with him, we decided it was the right thing to do.
"Yes, he is involved in a situation that is not normal. And it was a surprise that this has happened.
"But we have no worries about him playing because he is a very good professional. He has been training well and he will be thinking only about football.
"I want us to keep the momentum we have built up and, hopefully, he will perform as well as he has been playing recently and continue scoring goals.
"If he just focuses on football it will be easier for him, too. He needs to do things the way he would normally. All the staff are behind him 100 per cent because he explained everything to us and we know he's a nice lad."
England star Gerrard, 28, will have plenty of other first-team regulars to keep him company as Benitez has pledged to field a strong team.
He added: "We will make changes but, as we have a strong squad now, we can do it without weakening the team. That was not always the case.
"We will be trying to win the cup. We're in three competitions and they're all important to us."