The Cats suffered a huge blow when Stewart was ruled out of the season decider under concussion protocols, after he was hurt in a tackle during the preliminary final.
Fellow defender Jack Henry is also in some doubt with an ankle injury sustained during the rousing 30-point win over Hawthorn.
But Guthrie, who stepped up with a game-high 10 intercept possessions against the Hawks, believes the depleted Cats' back-line can hold up when it matters most.
"It's tough when you lose one of your best players like Stewy," Guthrie told AAP.
"I'm hoping Jack will be right to go and I'm sure he'll lift because it's a grand final.
"But it's a collective effort and I think some of those young guys like Connor O'Sullivan that stood in for us were really important for us.
"What's happened has happened and we'll look to rely on all those guys to make up the slack and work around them."
Geelong coaches and players have offered their support to Stewart in what Chris Scott described as a "shattering" scenario for the five-time All-Australian.
💙� pic.twitter.com/MEwiO415zE— Geelong Cats (@GeelongCats) September 20, 2025
Stewart addressed the situation on Saturday via social media.
"Obviously shattered with what happened last night, but so grateful and overwhelmed with all of the love and support I have received by so many," Stewart posted on Instagram.
"Couldn't be more proud of this group and to be a part of this amazing club is something that I truly cherish. How bout them Cats! LFG."
Max Holmes was the hard-luck story in Geelong's 2022 premiership year, not risked for the grand final after injuring his hamstring the previous week.
And Guthrie is another of those teammates who have a sense of the emotion Stewart is going through.
The 27-year-old was in his fourth season when he was left out of the 2020 decider, named among the Cats' emergencies for the 12th time that season.
"I'm feeling massively for Stewy. It's pretty tough for him, along with a number of other guys that will miss out," Guthrie said.
"I've been on that side of it as well and I know how tough it is.
"I'll try to rally around some of those guys because I know it's a lonely feeling.
"You don't want to be over the top and get in their face and over-check how they are, but I'll wrap my arms around them."
Guthrie emphasised Henry's importance to Geelong, lauding the key back's courageous performance against Hawthorn.
Henry was forced off the field before Stewart, who was then subbed out while his teammate was receiving medical treatment.
Henry returned to the action after quarter-time and marked dangerous Hawks veteran Jack Gunston.
"Having Jack get back out there was big for us," Guthrie said.
"You could tell he was a little bit hampered but having him there to structure us up was huge.
"He's one of our most important players."
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