And every MLS match is a chance for current national team stars to establish themselves and for other new faces to emerge, sliding up or down the pecking order for US head coach Bruce Arena or Canada's Octavio Zambrano based on how they play.
We're here to keep track of whose stock is rising and whose is falling after Week 18:
US national team
Matt Polster – The Chicago Fire right back was left off of Bruce Arena's initial 23-man Gold Cup squad, but is doing everything he can to draw attention for a recall in the knockout stage. 715423280" tabindex="0">On Saturday, Polster notched two assists, giving him three in the last two games. And since he took over at right fullback on 715423281" tabindex="0">May 17, the Fire are 7-0-1 with six clean sheets.
C.J. Sapong – As detailed by Armchair Analyst Matt Doyle, Sapong is the straw that stirs the Philadelphia Union's attacking drink. His early spot kick winner against New England gave the 28-year-old forward nine goals this term, matching his career best through just 17 games.
Steve Birnbaum – It's been a tough season for the D.C. United center back, who has only marshaled the DC back line to one clean sheet after opening day (and that was back in May). The Black-and-Red have leaked multiple goals in half of his 14 starts, including in Saturday's loss at Montreal, when he neglected to close down Blerim Dzemaili on the home side's winner.
Benny Feilhaber – The veteran Sporting Kansas City playmaker (who failed to make Arena's preliminary Gold Cup roster) did manage to make a quick return from an ankle injury caused by a nasty Week 17 tackle. However, Feilhaber has now not registered a goal or an assist for Sporting KC in six league games.
Canada national team
Will Johnson – The Orlando City spitfire has helped his new team maintain its upper-table standing as the Lions look to make the MLS Cup Playoffs for the first time. On Friday night, Johnson capitalized on a goalmouth scramble to bag the winner at Real Salt Lake as the Lions snapped a six-game win drought away from home. He is looking like a fair bet to add some experience and grit to midfield if Canada can reach the Gold Cup knockouts.
Ashtone Morgan – A Toronto FC player that has not suited up for Canada since 2015, Morgan had the chance to make a case for future inclusion with his first MLS start of the season this past weekend against FC Dallas. Unfortunately, he was a spectator on the through ball that set up Roland Lamah's decider and managed but three positive passes in the attacking end.