Allan Saint-Maximin has posted a picture of himself suggesting he is still recovering from his injury.
Eddie Howe said he hoped that the former Nice winger's injury was not "too serious" after it forced him to miss the trip to West Ham at the weekend.
United were still not ruling out his involvement against Brentford yesterday but Saint-Maximin has posted an Instagram stories message reading: "Rehab in progress" with the winger seemingly still in Monaco.
Newcastle always stressed that they would not risk Saint-Maximin if he wasn't 100% fit after a knock on his calf from the 1-0 win over Aston Villa meant he missed training last week.
Howe said: "Maxi got a kick on his calf against Aston Villa, I think you saw him limping towards the end of the game.
"He didn’t train this week. We hoped he’d be fit but obviously, he didn’t make the game.
"Hopefully, nothing too serious with Maxi but it was enough to keep him out today."
Saint-Maximin has been in France and posted pictures from Monte Carlo after working with sports physiotherapist Alexandre Baccili.
Eddie Howe will update the media on Friday morning on the status of the winger.