The former Leeds and Brentford midfielder has proved a big hit since signing for the Pilgrims on a short-term deal in October.
But, despite Argyle boss Derek Adams wanting to retain Diagouraga’s services, the 30-year-old is expected to move on after the visit of League One’s bottom side.
Midfielder Jamie Ness is still working his way back to full fitness following a calf injury.
There could be three new faces in Bury’s starting line-up.
Goalkeeper Connor Ripley, defender Peter Clarke and striker James Hanson have all arrived on loan to the bottom-of-the-table Shakers.
Boss Chris Lucketti has seen loanees Alex Whitmore, Jordan Williams and Mihai Dobre all return to their parent clubs, though defender Whitmore is the only one of that trio to have played in the past month.
Stephen Dawson, Danny Mayor and Nathan Cameron (all knee) will all come back into contention for starting spots but Jermaine Beckford and Joe Murphy (both knee) are out.
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.