Veteran midfielder Britton has suffered from groin and pelvis injuries in the last few months and not featured since October 21.
Andre Ayew and Andy King are both cup-tied as Swansea manager Carlos Carvalhal plans to rotate his squad again with Premier League survival his main priority.
Sheffield Wednesday pair Liam Palmer and Almen Abdi will both return to contention. Defender Palmer has been sidelined for three games due to an unspecified problem, while midfielder Abdi (knee) has been out since the end of December.
Jos Luhukay is still contending with an extensive injury list with midfielder Ross Wallace (knee), the latest casualty, waiting to learn whether he requires surgery.
Cameron Dawson is expected to start in place of Joe Wildsmith in goal, while Barry Bannan, Tom Lees, Keiren Westwood, Joost van Aken, Kieran Lee, Sam Hutchinson, Marco Matias, Jordan Thorniley,Gary Hooper, Fernando Forestieri andSteven Fletcher all still out.
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.