The former Argentina goalkeeper spent four years at Chelsea before leaving in 2021.
Caballero was assistant manager to Enzo Maresca at Leicester City last season and will follow him to Chelsea, says the London Evening Standard.
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Foxes first-team coach Danny Walker, goalkeeping coach Michele De Bernardin, fitness coach Marcos Alvarez and analyst Javier Molina Caballero could also join Maresca at Stamford Bridge.
Maresca is expected to be named Chelsea manager this week.