Filipe Luis is in danger of missing the World Cup after suffering a broken leg during Atletico Madrid's Europa League clash with Lokomotiv Moscow.
The Brazil international was substituted after 62 minutes of Thursday's second-leg tie, which Atleti won 5-1 to progress 8-1 on aggregate, after being left writhing in pain following a last-ditch challenge with Lokomotiv forward Eder.
Having been caught by the striker's follow-through, Filipe Luis left the pitch on a stretcher, with coach Diego Simeone expressing his concern for the defender in a post-match interview.
Atleti's fears were realised following checks on their return to Madrid, the LaLiga club confirming the details of the 32-year-old's injury on Friday.
"Filipe Luis underwent radiological tests as soon as he arrived in Madrid, which have confirmed that he suffered a fracture of the fibula of his left leg," a statement read.
The extent of the fracture - and how long Filipe Luis will be sidelined for - remains unclear.
Should he be unavailable for the tournament in Russia then Brazil will not be short of options at left-back, with Real Madrid's Marcelo and Juventus' Alex Sandro the likeliest pair to be selected in Filipe Luis' absence.