The Spanish side go into the week on the back of a 2-1 La Liga defeat to Barcelona, and while the focus has quickly shifted to Europe, preparations have been far from smooth.
Jose Maria Gimenez has emerged as the latest doubt after picking up calf discomfort following a knock in that weekend loss. With only a couple of days to recover, his availability remains uncertain heading into the midweek trip.
He joins a list of concerns for Diego Simeone. Jan Oblak and Marc Pubill are still being assessed, while Pablo Barrios has already been ruled out of Wednesday's encounter.
Despite Gimenez's well-known determination to play through pain, Atletico are expected to take a cautious approach. The timing is critical, with the second leg coming less than a week later and a Copa del Rey final against Real Sociedad also looming later this month.
Simeone is unlikely to gamble on the defender's fitness, especially with bigger tests still to come. In his absence, Robin Le Normand and David Hancko are expected to form the central defensive partnership, while Clement Lenglet remains an alternative option.
With Monday offering limited time for recovery and preparation, Atletico must make key decisions quickly. Their Champions League ambitions remain alive, but injuries are threatening to derail momentum at a crucial stage of the season.
Arsenal were handed a major lift ahead of their Champions League quarter-final first leg against Sporting Lisbon on Tuesday, with Gabriel Magalhaes returning to full training today.
Harry Kane is expected to lead the line for Bayern Munich in their crucial UEFA Champions League clash against Real Madrid, despite recent concerns over his fitness.
Christian Norgaard has called on Arsenal to respond quickly after their FA Cup quarter-final defeat to Southampton, insisting the squad must shift focus to the challenges ahead.
The Catalans 2-1 win over 10-man Atletico Madrid was enough to open the gap to Real Madrid in LaLiga to seven points after Los Blancos were beaten by Mallorca.
