The Argyle boss is hoping Benin international Reda Johnson's departure for the African Nations Cup can be delayed so he can feature against the Royals at Home Park.
If not, fit-again Chris Barker and Hungary international Krizstian Timar are on standby.
Mariner can recall on-loan Cardiff right-back Darcy Blake, whose place went to Karl Duguid on Saturday because Blake was not permitted to play against his parent club as part of his loan switch.
Goalscorer Gary Sawyer was recalled at left-back in place of Shane Lowry, whose loan spell from Aston Villa has ended, while there was an instant recall for Luke Summerfield in midfield.
Summerfield has just returned from a successful three-month loan stint with Leyton Orient and went straight into the starting XI as Duguid was deployed at right-back.