MADRID, Nov. 16 (Xinhua) -- Atletico Madrid could be without goalkeeper Jan Oblak for a period after Slovenia's national team coach Matjaz Kek revealed the shot-stopper had suffered a physical issue during Saturday's 2-0 World Cup qualifying defeat to Kosovo.

Kek confirmed in his post-match press conference that Oblak would miss Tuesday's match against Sweden as he returns to Spain for medical tests.

"He had a problem before the match started, and it has worsened. I think someone else will play against Sweden," Kek said.

"I hope Jan hasn't sustained anything serious and that he can return to play as soon as possible," the Slovenian coach added.

Atletico Madrid manager Diego Simeone will likely share those concerns, as Oblak has played every minute of Atletico's 16 official matches this season. The team faces a tough schedule heading into the Christmas break, with upcoming matches including a visit to Getafe, a crucial Champions League game against Inter Milan, and a midweek fixture away at FC Barcelona on Dec. 2.

Argentine goalkeeper Juan Musso has proven himself as a reliable backup, but Oblak's status as Simeone's first-choice goalkeeper since joining the club in 2014 underscores the trust the coach places in him.