The Madrid club announced the news this Tuesday in a press release.
“He has an overload (muscle) and tomorrow he will have exams. We preferred to leave him to rest,” Madrid coach Carlo Ancelotti told the press, while specifying that Lucas Vazquez would replace him.
“The player is fine and we don’t think it’s anything serious,” he said.
Carvajal is also likely to miss the Madrid derby against Atlético Madrid at the Wanda Metropolitano on Sunday.
Ancelotti also confirmed that Luka Modric was ready to start against Union Berlin. The midfielder had been a substitute in four of Madrid's first five La Liga matches.