The striker was handed his first start since his summer transfer to Merseyside in defeat at Aston Villa on Saturday, putting in a hard-working shift before being substituted in the second half.
And Benitez has given an update on the 32-year-old's condition and how well he might have recovered ahead of the League Cup clash.
The manager remarked: "We have to explain. Our fans are clever and they understand the situation, we needed to bring a player in with experience in the Premier League who could be a back-up.
"But he was not playing for four months, so we were not expecting he could play a full game so quickly.
"He is training hard and doing well. He has recovered well and he will be ready.
"But the problem is when you are not fully fit, every time you put him on the pitch, you have to see how much he needs to recover.
"He is quite positive and training well so I expect he can give us what we are expecting from him."
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