Maguire's current deal runs until summer, having had a one-year option triggered at the beginning of this year, and Casemiro's contract also expires at the same point, albeit the Brazilian has an optional year still available to the club.
The pair have been crucial to the first team under Amorim, despite Maguire being forced to the sidelines in recent weeks with an injury.
Given their contributions so far this season, Ruben was asked whether any decision had been made on their futures at this stage, in his pre-match press conference previewing Newcastle United's visit to Old Trafford on Boxing Day.