Both teams head into this one on a rough patch with just one combined victory between them from their last seven games apiece.
Match preview
Portland Timbers failed to win away from home for the fifth game running following a 3-2 defeat against San Jose Earthquakes at the PayPal Park on Thursday.
Giovanni Savarese's men opened the scoring through Cristhian Paredes before goals from Jackson Yueill and Jamiro Monteiro turned the game on its head, only for Bill Tuiloma to restore parity in the early exchanges of the second period after which Monteiro grabbed his second of the match 10 minutes from time to decide a thrilling contest.
As a result, The Timbers have dropped to 10th place in the Western Conference but remain level on points with Houston Dynamo in the race for the last playoff spot.
Next up is a clash versus an opposing side with just one victory in the last six meetings between the teams dating back to 2016.
However, that solitary triumph did come in the most recent encounter last May when Monday's hosts fell to a heavy 3-0 defeat.
Philadelphia Union played out a second consecutive share of the spoils following a goalless stalemate against Inter Miami on Thursday.
Jim Curtin's men were guilty of wastefulness in front of goal as they had the bulk of the chances to break the deadlock in what was a very open match at the Subaru Park.
Nonetheless, The Union remain top of the Eastern Conference but have now seen their lead over second-place New York City cut down to one point.
Having failed to come out on top in any of their last four away outings, Monday's visitors will be keen to get back to winning ways on the road.
Portland Timbers Major League Soccer form:
Portland Timbers form (all competitions):
Philadelphia Union Major League Soccer form:
Philadelphia Union form (all competitions):
Team News
Portland's Felipe Mora still awaits his first outing of the current campaign as he continues to recover from a knee problem.
Meanwhile, midfielder George Fochive has not featured much either having spent the last 12 games on the sidelines.
Philadelphia Union could be without the services of Julian Carranza, who was absent from his side's last outing due to a knock.
Twenty-seven-year-old Mikael Uhre is also unavailable for this weekend's visitors through a foot injury.
Having directly contributed to nine goals already this term, Daniel Gazdag is on the verge of matching his entire tally from last season (ten).
Portland Timbers possible starting lineup:
Ivacic; Rasmussen, Zuparic, Tuiloma, Bonilla; Paredes, D.Chara, Y.Chara; Moreno, Loria, Nathan
Philadelphia Union possible starting lineup:
Blake; Mbaizo, Glesnes, Findlay, Wagner; Elliott, Bedoya, Flach; Gazdag, Burke, Santos