The hosts currently occupy third spot, having won three of their last four games, while their opponents sit just one point behind with a game in hand.
Philadelphia come into this game in a strong run of form, having not lost any of their last six league outings, collecting 14 points in that time.
Before the recent three-week break at the beginning of June, they had recorded back-to-back victories, firstly defeating DC United 1-0 in Washington thanks to Kacper Przybylko's goal on the stroke of half time.
The Union looked set to fall to a defeat upon their return to action on Sunday though, as they were losing 2-0 away against Atlanta United going into the final 10 minutes, as Przybylko scored an own goal before Anton Walkes doubled the hosts' lead in the 82nd minute.
However, Jim Curtin's men did not go down easily, as they immediately pulled a goal back through Cory Burke before centre-back Jakob Glesnes rifled in a 93rd-minute equaliser from long range to snatch a vital point for his side.
That saw them remain in third spot in the Eastern Conference, while sitting level on points with second-placed Orlando City and one point ahead of Wednesday's opponents in fourth spot.
They will look to pick up another important victory on Wednesday to stretch that gap between themselves and the chasing pack, while their visitors will aim to take three points home to leapfrog Curtin's side.
Before the recent international break, Columbus Crew started to build momentum with consecutive wins, first defeating New York City 2-1 away from home as Lucas Zelarayan netted a brace in the final 10 minutes to snatch all three points, after their hosts had led for the majority of the encounter.
They then won by the same scoreline at home to Toronto, as Luis Diaz and Gyasi Zardes got on the scoresheet before Ayo Akinola pulled a goal back for the visitors early in the second half, but they may have been concerned that the break would halt their improvement.
That turned out not to be the case, though, as the Crew defeated Chicago Fire on home turf last time out upon their return to league action.
A Zardes brace inside the first half meant they were in the driving seat throughout, and they stayed in control for a comfortable 2-0 victory, making it three consecutive MLS wins for Caleb Porter's men.
That run has seen the Ohio outfit rise to fourth spot in the Eastern Conference, and they are quickly gaining momentum in their bid to retain the title, now comfortably inside the playoff spots.
With Wednesday's opponents just one point ahead, having played a game more, the trip to Philadelphia presents a great opportunity for Porter's men to break into the top three, helping their playoff draw if they are able to remain at the top end of the division for the remainder of the regular campaign.
Philadelphia Union come into this game without important midfielder Jose Martinez, who is away on international duty with Venezuela at the Copa America.
Their line will be led by Kacper Przybylko, who has been in clinical form this season, netting eight goals in 13 appearances in all competitions.
They will be led by experienced forward Gyasi Zardes, who netted a brace last time out to fire his side to a 2-0 win.
Philadelphia Union possible starting lineup:
Blake; Mbaizo, Glesnes, Elliott, Wagner; Bedoya, Flach, Monteiro; Fontana; Przybylko, Santos
Columbus Crew possible starting lineup:
Bush; Afful, Jonathan, Williams, Santos; Fraser, Nagbe; Etienne, Zelarayan, Matan; Zardes
We say: Philadelphia Union 1-1 Columbus Crew
With both sides coming into the game in strong runs of form, this could definitely go either way, and we cannot quite split them on this occasion.
Both teams have shown themselves to be solid defensively, which we see resulting in a low-scoring draw on Wednesday.