Atletico Madrid could be set to lose Jan Oblak for an extended period of time after the goalkeeper suffered a groin injury ahead of their Lokomotiv Moscow clash.
The club's official site confirmed that their number one shot stopper faced a spell on the treatment table after he picked up the problem before Thursday's Europa League game against the Russian outfit.
Oblak's absence from the team will be a huge blow to Diego Simeone's side, with the 25-year-old playing a key role in Atleti's defensive resilience that has seen them ship just 12 goals in 27 La Liga matches so far this term.
Atletico confirmed that Oblak would be unavailable in the immediate future via a statement, but suggested that further tests were needed before they could categorically say how long he'd be out of action for.
The statement read: "Today, 9 March, Jan Oblak underwent medical exams and was diagnosed with an injury to his left gluteus.
"He had been called up for our Europa League match against Lokomotiv Moscow, but was dropped last minute due to some discomfort in his gluteus.
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"Our goalkeeper is pending future developments to determine when he can be available again."
Oblak was also thought to be soldiering on with a suspected hand injury but he had been managing that knock through games until his groin flared up ahead of the Lokomotiv showdown.
Ooh noo... Get well soon oblak— ACEP ABDIYANSA (@ACEPABDIYANSA) March 10, 2018
The Slovenia international has been Simeone's go-to choice in goal since Thibaut Courtois ended his three-year loan spell in the Spanish capital, and has been instrumental in the success that Simeone has delivered.
Oblak has kept a remarkable 85 clean sheets in just 147 appearances for Los Rojiblancos and has only been breached in Spain's top flight four times since the turn of the year.
Axel Werner is expected to replace Oblak inbetween the sticks during his absence after Atletico allowed original backup keeper Miguel Angel Moya to leave for Real Sociedad in February.