The striker returned to full training last week after a long-term injury issue from his time on loan with Blackpool last term kept him out of pre-season.
Benitez admitted that Simms is not yet ready to come back to the team after his injury lay-off, but the striker was hugely excited to be involved with the senior squad at the weekend.
The manager remarked: "I will tell you something more. It is an interesting one.
"We were training the day before (the Aston Villa game) – maybe some people don't realise how difficult it was – we lost Richarlison and Coleman during the training session.
"We thought maybe Richarlison could do it but he was not capable.
"I went to talk to Marcel about the situation, Simms who'd had a couple of training sessions was there. I said, 'Are you happy to go, are you ready?'
"He said: 'Yeah, yeah, I am ready'. So after just a couple of training sessions after some months injured, we had to take him.
"The lad was really happy and excited (to be involved). But we knew he was not ready and is still not ready."
Benitez added: "He showed in the training sessions that he can score goals. He is a big lad and we were working on his movements a little bit.
"But we haven't had too much time, so I'm pleased because after some months he has the desire and was convinced he could help the team.
"Even when I was talking with (Anthony) Gordon to make a substitution (at Villa), he was saying, 'Me, me', he was excited.
"That is positive. But we have to keep working with him [Simms].
"I saw some videos of him and in the training sessions I saw him, he can score goals and, hopefully, if he can improve his movement, you never know, he is an option for us.
"If we recover the others, he needs time to play, but I am happy with his attitude."