The visitors also enter the contest in impressive form after a fifth straight win in all competitions helped them lift the US Open Cup in midweek.
Match preview
Philadelphia are guaranteed a place in the post-season, but they are still looking to make sure they clinch first position in the Eastern Conference.
Although second-place Montreal have a game in hand, the Union enjoy a comfortable eight-point cushion at the top of the standings.
After thrashing both DC United and Colorado Rapids 6-0 in consecutive games, Philadelphia swept aside Atlanta United via a 4-1 scoreline.
They followed three comprehensive wins with another victory last weekend as goals from Mikael Uhre and Daniel Gazdag helped Philadelphia claim a 2-0 away win over New York Red Bulls.
Having avoided defeat at Subaru Park this season, Jim Curtin's side have the chance to clinch an eighth consecutive home victory on Saturday.
Like their hosts, Orlando will head into Sunday's encounter in a confident mood after winning their last five competitive matches.
In their latest outing, the Lions won their first trophy as an MLS side courtesy of a 3-0 win over Sacramento Republic in the US Open Cup final.
Orlando's USL Championship opponents upset three MLS teams to reach the final, but they could not beat a fourth, with a Facundo Torres brace and a Benji Michel strike guiding Orlando to cup glory.
After making history in midweek, Orlando will turn their attention back to MLS action where they will look to cement their place in the playoffs.
Oscar Pareja's side are four points clear of eighth-place New England, but in their final six games, they will attempt to improve on fifth position.
Philadelphia Union Major League Soccer form:
Orlando City Major League Soccer form:
Orlando City form (all competitions):
Team News
Philadelphia have no reported injury concerns ahead of Saturday's contest, although they could make a couple of changes.
Alejandro Bedoya dropped down to the bench last weekend, but the midfielder could come back into the starting lineup to replace Matthew Real.
There could also be a return to the side for Julian Carranza, who will be looking to add to the 14 goals he has scored this season.
As for Orlando, they are unable to call upon Alexandre Pato and Joey DeZart due to knee problems, while a thigh injury will prevent Jack Lynn from featuring.
Robin Jansson was an unused substitute in midweek after missing the previous three matches through injury, and the defender is expected to be on the bench once again on Saturday.
After top-scoring for Orlando with nine MLS goals this season, Ercan Kara will continue to lead the line for his side.
Philadelphia Union possible starting lineup:
Blake; Harriel, Glesnes, Elliott, Wagner; McGlynn, Flach, Bedoya; Gazdag; Carranza, Uhre
Orlando City possible starting lineup:
Gallese; Ruan, Schlegel, Carlos, Moutinho; Urso, Araujo, Pereyra; Torres, Michel, Kara