Diego Simeone said Monday he is awaiting news on Luis Suarez's recovery from Covid-19 as Atletico Madrid prepare for the Champions League visit of already-qualified Bayern Munich.
The European champions thrashed Atletico 4-0 in Munich in October, but travel to Madrid for Tuesday's game without a host of stars including Robert Lewandowski.
Simeone was coy over whether Uruguay forward Suarez would be back from his virus-enforced layoff for Tuesday's matchday five encounter, saying that he was waiting for an update on his condition.
"This virus is strange, maybe tomorrow he could be negative and be in good condition, he is training, we will have to wait to see what happens," Simeone said.
"I spoke with him yesterday. He wants to be with the team, but the most important thing is that he is well and that he returns to normal ... if he does not play tomorrow he will play on Saturday (against Real Valladolid)."
Atletico's campaign in Europe's top club competition is in the balance, with the La Liga side second but a full seven points behind Bayern and Lokomotiv Moscow lurking two points back in third.
Lokomotiv host bottom side Salzburg in an early kick-off and if they win will move second before Atletico kick off in Madrid.
European champions Bayern meanwhile will be without Lewandowski, club captain Manuel Neuer, and midfielders Leon Goretzka and Corentin Tolisso, coach Hansi Flick said.
Flick said Tolisso was not fully fit but might be back to face RB Leipzig at the weekend, while Alexander Nubel would start in goal in place of Neuer.
He added that he would make decisions on the starting line-up ahead of the game on Tuesday.
"I'll wait until tomorrow and then go through who's in a good mood. Then we'll see who's playing."
Bayern have not lost in the Champions League since March 2019 and have won their last 15 games in the competition.
"At the moment we are not winning any beauty prizes, but the team is able to fight for 90 minutes. And that without much preparation," said Flick.
"We played through last season. We are satisfied with what we have achieved and we are doing well, but there are still big games to play in the next two-and-a-half weeks."
Javi Martinez joined Flick at the press conference and confirmed he was still thinking of leaving Bayern.
"In the summer, I was thinking: 'If an offer comes that is good for me and the club, I will move'," the 32-year-old Spaniard said.
"Playing another year for Bayern is very good. But I would like to try something new before I end my career."