Shelvey has been sidelined for almost a month with a thigh injury.
The problem also troubled him in pre-season – the midfielder sat out of the friendly against Braga early last month – and manager Benitez, while "optimistic", will make a late decision on Shelvey.
"He's been carrying the problem for a while," said Benitez. "He wanted to keep playing, because he has the quality.
"But I remember one session where he couldn’t kick the ball as long as he liked so he stopped. I told him to stop. Hopefully, this time, with the international break it has given him long enough.”
Shelvey has missed Newcastle’s last two Premier League games.
Winger Matt Ritchie, meanwhile, sat out the Manchester City fixture before the international break with a knee problem.
“We have had Jonjo training, and Ritchie’s still with the physio, but they’re pushing,” said Benitez. “These two players are the kind of players that you have to stop them, because they want to play and they’re working really, really hard to be there.
“So, we will see. Still, we have some time, but at least Jonjo was training. If we don’t have any problems, he can be there. It’s too soon to say ‘yes’, but I’m quite optimistic.
“Jonjo’s the kind of player who wants to play in every game, and he has been training, but at the same time there’s a problem.
“The last time he was pushing and pushing, we could see in training he wasn’t fully fit. He wanted to play – he was telling us he could.
“We don’t talk about his quality, we talk about his fitness.
“He has the quality to do it, but he has to be fit, because we play against another top side who moves the ball very quickly.
“Hopefully, this time, with the international break, it has given him long enough.”