Nicolas Raskin, Moussa Sissako, and Michael-Ange Balikwisha all tested positive after Tuesday tests, as did goalkeeping coach Jan van Steenberghe.
All four are in quarantine, as are Damjan Pavlovic and Abdoul Fessal Tapsoba, who live with Sissako.
Their chances of facing Rangers depend on the results of further screening.
Kemar Roofe, who was playing in Belgium with Anderlecht last season, has missed Rangers’ past six games with injury.
What do we know about Standard?
Like Rangers, Liege came through three one-off matches to reach the group stage with Bala Town, Vojvodina and MOL Vidi all beaten at Stade Maurice Dufrasne.
Selim Amallah scored in all three ties, including a double against Vidi, and the Moroccan midfielder is Standard’s top scorer in all competitions this term with six.
After placing fifth in their curtailed 2019-20 Jupiler Pro League campaign, Liege manager Michel Preud’homme resigned another former goalkeeper, Frenchman Philippe Montanier, was appointed as his replacement.
They are third in the league after nine fixtures, a point behind Club Brugge and Charleroi.
What they said
Standard Liege manager Philippe Montanier: “We are aware that in one week, the cases of coronavirus have exploded and we are no exception to the rule. The players are very careful, whether at the club or outside, so we remain rather calm.
“The example of Club Brugge is a good example. The Brugeois left without three starters at Zenit St Petersburg and they won. It is a good omen. We would have preferred to have the absent players with us but, as always, it is the group which we have at present which will have to make up for the absentees.”
- These sides have met in Europe once previously, Standard eliminating Rangers in the European Cup quarter-finals in 1961-62.
- Rangers’ last game in Belgium was a 1-1 draw with Club Brugge in the group stages of the 1992-93 Champions League.
- Standard have failed to emerge from the Europa League group stages in each of their past five attempts.
- Reaching the last 16 last season was the furthest Rangers have gone in the competition since 2010-11.
- Alfredo Morelos has scored eight goals in 14 games in the Europa League, although he has failed to score in his past three.