The onus is more on the away side to claim all three points heading into this one, but the home side are not over the line yet in the race for a knockout berth.
Match preview
Seattle Sounders turned on the style late on to claim a thrilling 2-0 victory at the expense of Minnesota United in Saturday's opening cup involvement.
The game was level heading into the final three minutes of regulation time after which Jordan Morris and Paul Rothrock netted to get the job done for Brian Schmetzer's men.
That was a perfect response to losing 3-0 against Los Angeles FC in their last league outing, which remains the Rave Greens' only defeat since early June.
Seattle Sounders have also won eight of their 10 outings in that time and are proving to be solid at both ends of the pitch, with five clean sheets recorded and 18 goals scored.
While they sit top of their Leagues Cup group at the moment, Sunday's hosts will need to avoid defeat here to avoid being sucked into any scrap for survival.
Schmetzer's men crashed out in the group stages of last year's tournament with zero points from their two matches, and they now have the opportunity to go full circle with maximum points this time around.
Necaxa fell to a narrow 1-0 defeat against Minnesota United when the teams went head-to-head at Allianz Field on Wednesday.
Despite dominating for large spells of the contest, Eduardo Fentanes's men failed to find the back of the net for a third time in five matches since scoring at least one goal in 16 straight games.
Necaxa's attacking woes have unsurprisingly coincided with a drop in form, as Los Rayos have won just one of their last six matches across all competitions.
They currently sit bottom of Group Six, three points behind Minnesota in second place, meaning that only a victory on Sunday would guarantee progress into the next round.
The visitors have not fared well on the road lately with no wins in five matches dating back to April, leaving them with work to do in their trip to Washington.
Seattle Sounders Leagues Cup form:
W
Seattle Sounders form (all competitions):
W
W
W
W
L
W
Necaxa Leagues Cup form:
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Necaxa form (all competitions):
L
L
W
L
D
L
Team News
Seattle Sounders' Jordan Morris has scored six goals in his last eight appearances and will be looking to deliver the goods once again.
Raul Ruidiaz was hauled off with an injury scare against Minnesota United, making the 34-year-old a major doubt to feature in this one.
Should Ruidiaz be deemed unfit to participate, Leo Chu could be handed a recall to the starting lineup for the home side.
Bryan Garnica returned to action last time out having served a one-match ban, and the forward is expected to retain his place in Necaxa's lineup.
Ricardo Monreal risks dropping to the bench here, having now failed to score for the visitors since April off the back of yet another blank.
Seattle Sounders possible starting lineup:
Thomas; Roldan, Ragen, Bell, Tolo; Paulo, Vargas; Roldan, Rusnak, Chu; Morris
Necaxa possible starting lineup:
Unsain; Mayorga, Oliveros, Montes, Martinez; Arce, Palavecino; Gomez, Paradela, Garnica; Cambindo
We say: Seattle Sounders 2-1 Necaxa
Compared to Necaxa, Seattle Sounders have less pressure on their backs leading up to this one, but a chance to keep their good run going should provide enough motivation.