After falling to a shcok 1-0 defeat to Real Betis at the Bernabeu last time out, Real will be desperate to get back to winning form and to try to close the gap on leaders Barcelona, a gap which is already seven points.
Real named their 19-man squad for the game on Friday, with the absence of Kroos the main talking point.
The German was unable to take part in training this week ahead of the game and has now been ruled out completely with a side strain.
Kroos joins Karim Benzema, Jesus Vallejo, Mateo Kovacic and Theo Hernandez on the sidelines, leaving Real boss Zinedine Zidane with a defensive headache at left-back, with Nacho expected to step in.
Zidane has picked the following 19 players for the La Liga clash: Keylor Navas, Kiko Casilla, Luca Zidane, Dani Carvajal, Sergio Ramos, Raphael Varane, Nacho, Achraf Hakimi, Alvaro Tejero, Luka Modric, Casemiro, Marcos Llorente, Marco Asensio, Isco, Dani Ceballos, Cristiano Ronaldo, Gareth Bale, Lucas Vázquez and Borja Mayoral.
#RMMovistar
— Real Madrid C.F. (@realmadrid) September 22, 2017
Los 19 convocados para el partido ante el @Alaves pic.twitter.com/dKi3sR4GqL