Tottenham are concerned over Son Heung-min's mental state ahead of their trip to Belgrade.
Spurs return to action in the Champions League on Wednesday night following their 1-1 draw with Everton at Goodison Park.
Son saw red for a late challenge on Andre Gomes, that led to the Everton midfielder suffering a fractured and dislocated ankle.
The South Korean star was visibly distraught by Gomes' injury and Tottenham have offered him counselling to help him get over the trauma.
There are doubts over whether he will be in the right mindset to travel to Belgrade with Spurs set to make late checks on him before making a decision.
Tottenham have appealed Son's red card after referee Martin Atkinson appeared to initially pull out the yellow card.
Son is expected to reach out to Gomes in the coming days, with the midfielder undergoing successful surgery on Monday.
There is no timescale on his recovery although initial suggestions are he could be out for up to a year.
Speaking after the draw, Son's teammate Dele Alli said: "He is devastated and in tears. It’s not his fault. Son is one of nicest people you’ve ever met.
"He can’t even lift his head up, he’s crying so much."
Son was consoled by Everton captain Seamus Coleman in the away dressing room at Goodison Park.
Harry Kane could return for Spurs against Red Star Belgrade after missing the clash through illness, while Totteham will hand late fitness tests to Jan Vertonghen and Erik Lamela.
