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:
5. LB: Dan Burn
With Tino Livramento and Lewis Hall still sidelined, Burn is expected to continue at left-back. | Getty Images
6. CM: Bruno Guimaraes
The Brazilian scored on his last St James' Park appearance, helping Newcastle to a 2-0 win over Nottingham Forest. | Getty Images
7. CM: Jacob Ramsey (in for Sandro Tonali)
With Tonali suffering from illness in recent days, Howe might be tempted to rest the Italian. Midfield is one of the areas Newcastle aren't short on bodies. | Getty Images
8. CM: Lewis Miley (in for Joelinton)
Miley has played his way into contention after making a positive impact off the bench at Brighton on Saturday. | Getty Images