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.
Reading will have striker Simon Church back for the trip to Home Park.
The Wales international missed the 1-1 draw with Swansea on Boxing Day as he served a one-match suspension but returns to the fold to take on the Pilgrims.
Brian McDermott will also wait on the fitness of Jay Tabb. Tabb missed out against the Swans with a calf strain sustained at Bristol City earlier in December and remains a doubt to take the right-back spot.
Fellow midfielder Brynjar Gunnarsson filled in at full-back against Swansea and McDermott is not concerned at using either player in the back four.
He said: "The last thing we want to do is put Jay out for any longer and we are not 100% sure if he will be fit. But Brynjar was outstanding and showed what a terrific pro he is."
Forward Noel Hunt is out for at least another few months as he recovers from knee surgery, but Brian Howard could be involved after he was surprisingly on the bench on Boxing Day - just a month after breaking his jaw against Derby.
Sporting Life