"Good Morning America" won't be left high and dry when Robin Roberts goes on medical leave in a couple months -- TMZ has learned, producers are arranging a star-studded list of substitutes to sit in for her.
As we reported, Roberts was diagnosed in April with myelodysplastic syndrome -- a serious blood and bone marrow disease -- and has already begun chemotherapy treatment ... before her big bone marrow transplant in a few months.
As for who made the temp list -- we're told producers will approach Diane Sawyer, Charlie Gibson, Barbara Walters, Chris Cuomo, Connie Chung, Joan Lunden and others. We're told each substitute will sit in Robin's chair for a full week, and each Friday the next star sub will be announced.
Given the nature of the operation, it could take Roberts 4 months to recover -- so the list will be long.
But here's the good news. Robin, we're told, is in good physical shape and the condition was detected very early, so the prognosis is "very good" and she could be back much sooner than the 4 month estimate.