The Broncos will host the Knights at Totally Workwear Stadium this Saturday in the NRLW's second elimination final.
The match could mark Ali Brigginshaw's final appearance, after Brisbane's captain was honoured following last Sunday's Round 11 clash.
Brigginshaw spoke to the crowd and received a framed career photograph before Warriors players and staff performed a haka.
That ceremony made the 29-year-old Upton realise her long-time teammate's retirement was imminent.
"With what happened on Sunday with the celebration and all, it really hit me," Upton told NRL.com.
"It hasn't felt real until all of that - she's not going to be there next year and she's always been there with me."
Upton said Brigginshaw had deliberately chosen to hold her farewell after Round 11, keeping attention away from Brisbane's finals campaign.
"Ali's pretty switched on and she wanted all that done last round, rather than running into finals," Upton said.
Brisbane are attempting to defend their 2025 title, while Upton and Brigginshaw prepare to share their final training sessions and matches.
Upton made her NRLW debut in 2019 and has played alongside Brigginshaw for five Broncos seasons, seven Jillaroos Tests and 10 Maroons Origins.
She said Brigginshaw's family, friends, chief executive Dave Donaghy and club officials made the farewell particularly meaningful.
"It was incredible and what she deserves - and as a team it can only galvanise us."
Brigginshaw leaves with 65 NRLW games, 13 Origins and 23 Tests, and Upton said she would miss her teammate's constant humour.
"She is very emotional. She's such a softie to be honest - she does wear her heart on her sleeve."