Pat Noonan's side could still finish as high as fifth if they beat DC, who will finish bottom of the Eastern Conference with the worst record across the entire league.
Match preview
FCC could have confirmed their place in the post-season for the first time in their history with victory at home to Chicago Fire last weekend but suffered a shock 3-2 defeat.
Goals late in the second half from Luciano Acosta and Brandon Vazquez were not enough as a Brian Gutierrez strike and a brace from Jhon Duran - as well as a red card for Cincy's Sergio Santos - gave the Fire the win.
A draw will be enough to progress to the playoffs, and the Orange and Blue have not found stalemates hard to come by this season.
Before the defeat against Chicago, they had been on a remarkable run of just one defeat in 18 games, but that did include 12 draws.
Cincinnati have never beaten DC in seven previous meetings, though, including defeat earlier this season, making Sunday's game anything but straightforward.
Sunday marks the end of an unspectacular campaign for DC United which has seen them pick up the MLS' Wooden Spoon as the worst team across both conferences.
The 1-0 defeat at CF Montreal last weekend courtesy of Donovan Pines's own goal - before he was later sent off - was Wayne Rooney's side's third consecutive loss.
Their home form has been the worst across the entire league, picking up just four wins from their 16 games so far, as well as conceding a joint-worst 29 goals.
DC will look to end the season on a high ahead of the off-season, which will be Rooney's first as head coach of the club.
DC United Major League Soccer form:
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D
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FC Cincinnati Major League Soccer form:
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D
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D
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FC Cincinnati form (all competitions):
D
W
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L
Team News
Santos will be suspended following that late red card last weekend, but that is the only new concern for Noonan to contend with.
Beckham Sunderland remains in the concussion protocol so he will not be available, and Kenneth Vermeer will not be back until after the playoffs have ended.
Allan Cruz was an unused substitute last weekend, but he should come back into the starting XI.
DC United will also be without the suspended Pines, and Taxiarchis Fountas will remain absent from the squad following the allegations of racist abuse by Inter Miami's Damian Lowe.
Jose Vazquez could come into the starting lineup in Pines's place, and Ravel Morrison could start in midfield behind Christian Benteke.
DC United possible starting lineup:
Ochoa; Palsson, Vazquez, Birnbaum, Guediri; Djeffal, Durkin; Rodriguez, Morrison, Berry; Benteke
FC Cincinnati possible starting lineup:
Celentano; Powell, Hagglund, Cameron, Miazga, Barreal; Nwobodo, Acosta, Cruz; Vazquez, Brenner