Just one place and one point separate the two in the table, with both sides desperate for a win to strengthen their position in the top seven.
Match preview
After a winless start to the campaign that saw the Union go three matches without a victory, Jim Curtin's side embarked on an impressive eight-match unbeaten run that saw the club rocket up the table.
Results have since stabilised and the Union now sit amongst the mid-table teams, yet Curtin's men are still well placed to reach the playoffs for the third consecutive year.
Disappointed to have been knocked out in the first round of last season's playoffs, despite topping not only the Eastern Conference table, but also the overall standings, the Union will be chasing their first Major League Soccer Cup title since becoming a franchise in 2010.
Further disappointment struck the U this week after they were knocked out of the CONCACAF Champions League semi-finals following a sombre 4-0 aggregate defeat to Mexican side Club America.
Now with just MLS to focus on, the side from Philadelphia will be looking to return to winning ways when Atlanta travel North to the Keystone State.
Unlike their opponents, Atlanta have no issue with chasing their first MLS Cup triumph, having lifted the trophy in their second season as a club in 2018.
Going on to win the US Open Cup in the following season, Atlanta suffered a grave decline in the disrupted 2020 campaign, finishing second from bottom in the Eastern Conference.
Having somewhat bounced back this season, the Five Stripes are another team involved in the tight chase for a playoff spot and will be wary of Philadelphia one spot below them.
Victorious in all but one of their last eight MLS fixtures, Atlanta will be confident of extending their winning streak, not least because of their strong form against Philadelphia in recent years.
Losing only once in their eight MLS meetings, Atlanta have been a thorn in the side of the Union on a number of occasions, yet Curtin's men did have the pleasure of knocking United out of the Champions League this season.
Toppling the 2018 MLS Cup winners 4-1 on aggregate, the Union will be keen to replicate their continental triumph when the two meet this weekend.
Philadelphia Union Major League Soccer form:
Atlanta United Major League Soccer form: