Eddie Howe has conceded he does not know if Allan Saint-Maximin will be fit before the end of the season.
The winger has missed the last four matches because of a hamstring injury and returned to his native France for treatment this month.
There had been hope Saint-Maximin could feature during Sunday's 6-1 victory over Tottenham.
However, he did not make that game and was again absent for Thursday's 4-1 win at Everton.
While Howe insists there has been no setback, he admits there is no guarantee the 26-year-old will return during the final six matches of the campaign.
'He won't be available for Sunday (at home to Southampton),' said Howe. 'Maybe the game after that (Arsenal, May 7), but there's no guarantee at this moment.
'I certainly hope he'll be fit before the end of the season, but with hamstring injuries, there's always that element of doubt.
'He's not had a setback, he just needs to build his fitness levels up and make sure he's fully fit before he comes back.'
Should Saint-Maximin fail to prove his fitness, there is a chance he could have played his last game for the club, with offers likely to be considered should they materialise.
His sale would boost the transfer fund ahead of a busy summer in which Newcastle are almost certain to be building a squad for the Champions League.
Howe continues to deflect talk of a top-four finish, but he said: 'I'm so proud of everyone connected with the club this year, with what we've given – players, staff, board, everyone, we feel really united at the moment.
'Things are going well, although we're not taking that for granted because we know how quickly it can change.
'There's a lot of hard work going in, and we need to not take our eye of the ball. But we're enjoying the feeling we're having and long may that continue.'