Sergio Ramos, Lucas Vazquez and Vinicius Junior scored the goals in the first leg at the Bernabeu, and the European champions will be looking to finish the job when they travel to Leganes on Wednesday night.
Los Blancos have a fairly extensive injury list at the moment, however, and Solari faces the tough task of picking a team for the trip to Leganes this week.
Here, Sports Mole takes a look at how an injury-hit Madrid could line up.
Out: Marco Asensio (muscle), Marcos Llorente (abductor tear), Gareth Bale (calf), Toni Kroos (abductor tear), Thibaut Courtois (hip), Karim Benzema (finger), Jesus Vallejo (hamstring)
Doubtful: Mariano Diaz (back)
One look at the injury list above shows Solari's problems when it comes to picking a team for this match.
Marco Asensio, Marcos Llorente, Gareth Bale, Toni Kroos and Thibaut Courtois all missed the clash with Betis, while Benzema picked up a fractured finger during Sunday's affair to join the injury list.
Jesus Vallejo would have been a certainty to start, but the defender limped out of Monday's training session with a hamstring problem and will now be unavailable.
Should Mariano Diaz fail to shake off a back problem, there is every chance that Isco could be handed a false nine role, with in-form Vinicius and Vazquez making up the front three for the European champions.
Castilla youngsters Manu Hernando, Jaime Seoane, Alex Martin, Martin Calderon and Gorka Zabarte all trained with the first team on Monday, meanwhile, and could be involved in the squad on Wednesday night.
Keylor Navas will start between the sticks though, while there should be first-team experience in the shape of Sergio Ramos, Nacho and Casemiro, with Federico Valverde and Cristo Gonzalez also pushing to be involved.