The legendary Los Blancos goalkeeper has been restored by Carlo Ancelotti for cup matches, in the Copa del Rey and the Champions League.
Diego Lopez has been between the sticks for league games, until Wednesday night's clash with Valladolid, to give Casillas more game time ahead of the Champions League final against rivals Atletico Madrid.
Casillas is not hugely likely to depart the club he loves, but whether he would be happy to continue along the same path next season is unknown.
If he were to leave Madrid, Ancelotti would have to bring in a replacement, either as an understudy to Lopez or to usurp him.
Here, we look at five possible replacements.