That may no longer be the case.
Brown told ESPN an "amazing camp" over the past few months has rejuvenated his career, and now he's having second thoughts about retirement.
"I still don't know for sure," Brown said. "I didn't expect myself to feel as good as I do right now, coming into this fight as motivated as I am and as driven as I am. I've just put a lot of things together mentally that have really propelled me and made me feel much better for this fight. I'm really happy to get in there and go perform.
"We're going to worry about whether it's my last fight next week, but right now I'm worried about Saturday only."
Brown, 36, has fought professionally since 2005. He has faced many top contenders in big fights but fell short of competing for a UFC belt. Brown is coming off three straight losses, most recently a head-kick knockout defeat to Donald Cerrone in December 2016.
Brown (20-16) said buildup of injuries over the years and a recent lack of determination to contend for a title were reasons for him originally to want to leave the sport.
"The No. 1 thing was the hunger, drive and motivation," the Ohio native said. "It's not that I haven't had the hunger and drive to fight, but the hunger and drive to go on a championship run like I did a couple years ago. I would not take no for an answer. I trained like an animal every day. Over the past year I haven't had that same hunger. I don't want to be a journeyman or fighting just to fight."
Brown said he has no exact timetable for a final decision, but expects to know by the end of 2017. Right now he just wants to concentrate on his matchup against fellow veteran Sanchez (27-10), who has split his previous six fights. Sanchez's last bout was a first-round KO loss to Al Iaquinta in April.
"I've always been a big fan of Diego's," Brown said. "I think we all know what to expect. He's going to come in and swing and brawl big and throw big punches or get a takedown. Either way, he's going to be aggressive, come forward and push the pace.
"I won't even think about [retirement] until after the fight. It doesn't really mean anything until it happens. I have to go out there and make it happen first. Right now I'm focused on performing at my best, and if I do that everything else will take care of itself."