Kroos underwent an antigen test on Friday morning which came out negative.
“Real Madrid reports that our player Toni Kroos is currently in isolation after being in contact with a person who has tested positive for COVID-19, although all tests carried out on the player have come back negative,” a club statement said.
Even if Kroos’ latest test is negative, as per the La Liga protocol, he will not be able to travel to Bilbao.
Kroos will only be able to join the team once he has an additional negative test in the coming days.
Kroos has been a key player for Zinedine Zidane, scoring three goals and setting up nine more in 42 appearances in all competitions this season.
Zidane gave Kroos a rest in Madrid’s 4-1 league win at Granada on Thursday in view of this weekend’s crunch game in Bilbao.
Madrid are second in La Liga, two points adrift of La Liga leaders Atletico Madrid with two games remaining.
Atletico host Osasuna on Sunday.