The two ever-presents were both absent from the squad to face Newcastle United at the weekend, as Spurs slumped to their second Premier League defeat in the space of a week.
Following that 2-1 loss, Antonio Conte revealed that the pair had sustained fatigue-related injuries, with Romero picking up a calf issue while Hojbjerg was having trouble with his thigh.
The Italian could not guarantee that the pair would be available for the visit of Ruben Amorim's side, telling the press: "Romero in the last two or three games, he arrived every day half and half to decide if he play or doesn't play.
"I think in the past we have taken risk. The players gave their availability to play otherwise honestly if the player doesn't want to play, I don't force them.
"Now after the game against United, he felt a lot of fatigue and then yesterday he felt fatigue in his calf. Before in his thigh, the right. Now left in the calf. Pierre it was the same because Pierre played every game, he played every minute and he was really tired.
"I don't know about Pierre and Cuti for Wednesday. I don't know the way they recover from this fatigue and this situation. If they have something, Romero in his calf or Pierre in his thigh."
Tottenham opened up a portion of their training session to the media on Wednesday morning, and neither Romero nor Hojbjerg were pictured during team practice.
Conte is set to give an update on the pair when he holds his pre-match press conference, but it is difficult to see the two players featuring on Wednesday night given their absences from training.
Tottenham are sure to be without Richarlison and Dejan Kulusevski once more, with the former still expected to remain sidelined for another couple of weeks with his calf injury.
Meanwhile, Kulusevski had briefly come back into training before Spurs beat Eintracht Frankfurt in the Champions League two weeks ago, having come back from the international break with a hamstring issue.
However, the Sweden attacker has suffered a major setback in his recovery, and Conte cannot guarantee that he will be able to play again before the World Cup break.
Tottenham sit top of Champions League Group D with seven points from four games, and victory over Sporting would be enough to guarantee them a place in the knockout stages.
The Portuguese side are not without their own concerns for the trip to North London, as Ricardo Esgaio and Pedro Goncalves are both suspended after receiving red cards against Marseille.
Sebastian Coates, Jeremiah St Juste, Luis Neto and Daniel Braganca are also out of contention for the third-placed visitors - who are level with Marseille and one behind Tottenham with six points - but goalkeeper Antonio Adan is back from a European ban of his own.