A cluster of high-profile players - including Diego Costa and Thiago Alcantara - have suffered worrying injuries in recent weeks that put their participation at the FIFA World Cup in jeopardy, while Victor Valdes will definitely miss out after undergoing knee surgery this week.
Radamel Falcao continues his rehabilitation from a knee injury and Cristiano Ronaldo was substituted during Real Madrid's 3-0 win over Borussia Dortmund in the UEFA Champions League in midweek with a minor knee problem.
"He (Ronaldo) has a minor problem, like many other players," Alonso said at a promotional event. "But it is true that the schedule is very tight.
"Since September we've been playing Wednesday-Sunday and finally the World Cup is approaching.
"Diego Costa has been injured, Marcelo has been injured, and there will be more injuries.
"We have to get a more sensible calendar.
"We started playing in the cup (Copa del Rey) in January and we don't have the rhythm other countries have."
