Playmaker Billiat is still nursing a knee problem, which kept him out of the 1-0 win at Golden Arrows last time out.
Winger Laffor remains sidelined with a foot complaint that will see him miss a third straight match for the Absa Premiership leaders.
Meanwhile, midfielder Lucky Mohomi is on the mend from a knee injury, while Zimbabwean striker Cuthbert Malajila is still making his way back from surgery.
Downs released a statement on their website, which reads: 'Mamelodi Sundowns take on Maritzburg United in a critical Absa Premiership clash minus some crucial players.
'Khama Billiat will miss the match as the Zimbabwean international is nursing a knee injury, which saw him also miss the previous match.
'Anthony Laffor is also still out, nursing a foot injury, which has kept him out since the Chippa United clash.
'Word from the team doctors is that Lucky Mohomi is recovering well from his knee injury. Cuthbert Malajila is recovering from his operation.'
Sundowns will host mid-table Maritzburg at Loftus Versfeld Stadium (19h30).
The Brazilians will end 2017 with visits from Bloemfontein Celtic and Cape Town City on December 16 and 19.