Reign will honour the veteran midfielder, with several activities planned around the stadium, including a commemorative photo booth and dedicated merchandise.
Several members of Fishlock’s family have flown out to the Pacific Northwest so they can be among the expected 16,000-strong crowd at Lumen Field.
“I don’t think I’ve had this many family out, ever. It’s been a little crazy,” Fishlock added.
“I’m not used to having little Rugrats running around everywhere, taking all of my spare energy that I need. But it’s been great.
“I will really be able to enjoy it post-game. I’m focusing on the match itself and (reaching the) playoffs to keep the season going a little bit longer, which would be nice.
“I’m extremely grateful and so appreciative of everybody showing out for me. Everything that the Reign has done has been undeniably incredible and beautiful.
“But without sounding ungrateful, I am still very much focused on the game itself. I’m sure post everything, it will hit me far harder than I’m allowing it to hit me right now.”
Fishlock’s retirement will close a chapter in Reign’s history, as she is the last of the club’s original three stars to step away, following Megan Rapinoe and Lauren Barnes.
It will also mark the end of an era for the league. She is one of the division’s most recognisable figures, and bounced back from a serious-looking injury to go out on her own terms.