D.C. United plays for the Eastern Conference top seed Saturday while the Fire play for next year in their road season finale at RFK Stadium.
United (16-9-7, 55 points) holds a three-point lead over second-place New England and would clinch first place with a victory or tie.
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The Fire (5-9-18, 33 points) hope to break a seven-game winless streak.
“It’s really important for us to stay focused on the coach’s message and end on a good note,” goalkeeper Sean Johnson said after last Friday’s 2-0 loss at Kansas City. “We owe it to ourselves and to our fans.”
Johnson has been the Fire’s most reliable player this season. He has played in all 32 regular-season game while recording seven shutouts.
But he could get Saturday off as Fire coach Frank Yallop told reporters this week that backup Kyle Reynish might get his MLS first start of the season.
United forward Luis Silva is out reportedly for four to six weeks after suffering a hamstring injury last week. He has 11 goals and four assists in 22 games.
Untied and the Fire have played to ties in two previous meetings this season.
The 2014 Fire have the fewest victories in franchise history and own the all-time record for ties in MLS with 18. They will close the regular season next Friday at home against Houston.