The Magpies were back in training on Monday morning following Saturday’s 2-1 defeat to Brighton & Hove Albion, with Tonali absent from the session.
It was later confirmed that the Italian is suffering from illness but will be given “every opportunity” to prove his fitness and feature against Jose Mourinho’s Benfica.
Newcastle head coach Eddie Howe said: “Bit of illness with Sandro, so he’ll be touch and go. We’ll give him every opportunity. He’s such an important player, we’ll use all the hours we can.”
With United again in the midst of a busy fixture period, midfield is one area Howe could look to rotate with Lewis Miley and Jacob Ramsey waiting in the wings.
Howe added: “Yeah, they have Champions League experience, but they're also very, very good players.
“I think we've got a really strong midfield this year, so if one player is missing, it's an opportunity for a very good player to come in and grab theirs. I thought both players did well when they came in on Saturday.”
Without further ado, here’s how we’re predicting Newcastle United to line-up against Benfica:
9. RW: Jacob Murphy (in for Anthony Elanga)
Anthony Elanga has struggled to hit the ground running, leading to calls to recall Murphy. | Getty Images
10. LW: Anthony Gordon
Gordon is the Magpies' top goalscorer in the Champions League this season with three goals in two games. | Getty Images
11. ST: Nick Woltemade
Five goals in six starts... can Woltemade continue his impressive form against Benfica? | AFP via Getty Images