The visitors, meanwhile, will book their place in the postseason if they can claim maximum points at Stade Saputo.
Match preview
Montreal's hopes of reaching the playoffs for a second straight season have been dented by a seven-game winless run.
After suffering consecutive defeats, Montreal played out draws against both Chicago Fire and Cincinnati, before losing back-to-back away games against Atalanta United and Orlando City.
Hernan Losada's side looked set to lose for a third consecutive game when Arthur gave Houston Dynamo a 10th-minute lead in Wednesday's home fixture, but the Canadian side managed to salvage a point thanks to Lassi Lappalainen's stoppage-time equaliser.
With two games left to play, Montreal are currently sitting in ninth position in the Eastern Conference, which would be enough to secure them a spot in the inaugural wildcard round.
However, they can ill-afford to drop points in Saturday's contest, with goal difference separating them from New York City, while 13th-placed Charlotte FC are two points adrift with a game in hand.
In contrast to their hosts, Portland are currently enjoying a fine spell of form after putting together a seven-game unbeaten run.
The Timbers took four points from meetings with Real Salt Lake and Seattle Sounders, before claiming four successive victories ahead of last weekend's trip to Los Angeles.
Despite taking the lead on two occasions against LA Galaxy, the Timbers required a 76th-minute equaliser from Felipe Mora to ensure the entertaining contest finished in a 3-3 draw.
With Portland sitting in seventh position and five points clear of 10th-place Austin, they will book their place in the postseason with a game to spare if they can claim their third away win of the MLS season.
Picking up all three points will be easier said than done, having failed to win any of their last four meetings (D2, L2) since recording a 2-1 away win in May 2015.
CF Montreal Major League Soccer form:
L
D
D
L
L
D
Portland Timbers Major League Soccer form:
D
W
W
W
W
D
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Team News
The hosts remain without the services of Robert Thorkelsson and Aaron Herrera, who are ruled out with ankle and adductor injuries respectively.
Forward Jules-Anthony Vilsaint is a doubt for the weekend after missing Montreal's last four matches with an ankle problem.
After coming off the bench to score a stoppage-time equaliser against Houston Dynamo, Lappalainen could be rewarded with a place in the starting lineup.
Portland, meanwhile, are unable to call upon David Ayala, Jaroslaw Niezgoda and Eryk Williamson, who are all sidelined with anterior cruciate ligament injuries.
Yimmi Chara and Evander are also doubts for Saturday's away trip due to hamstring and calf issues respectively.
Cristhian Paredes will have to be assessed after being forced off in the first half of the 3-3 draw with LA Galaxy.
CF Montreal possible starting lineup:
Sirois; Campbell, Waterman, Alvarez; Brault-Guillard, Saliba, Choiniere, Piette, Lappalainen; Opoku, Quioto
Portland Timbers possible starting lineup:
Bingham; Mosquera, Zuparic, McGraw, Bravo; Caliskan, Acosta, Moreno; Asprilla, Antony, Mora
We say: CF Montreal 1-1 Portland Timbers
Although Montreal have won their last two home meetings with Portland, the Timbers are unbeaten in seven MLS matches, and we think they will continue that run by taking a point from Saturday's trip to Canada.
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