The winless clubs meet at Norwood Oval in Adelaide in a Friday twilight fixture stoked by claims of a rift within the Lions' den.
"We expect nothing less than a fierce battle," Simpkin told reporters on Thursday.
Brisbane coach Chris Fagan has rubbished reports of an off-season trip to Las Vegas by a group of players triggering a split.
And Lions forward Zac Bailey is the latest Lion to reject the supposed ructions.
Lions coach Chris Fagan (right), with Joe Daniher at training, says there is no rift at the club. (Darren England/AAP PHOTOS)
"I wouldn't say there's a rift in the team, we're closer than ever at the moment," Bailey told reporters on Thursday.
"We put all that stuff to rest at the start of the week and our focus is on North Melbourne and hopefully getting the win."
Despite the denials, Simpkin said the Kangaroos were bracing for a rugged on-field retort from the Lions when both clubs seek to snap a three-game losing streak.
North's defence, a week after conceding a combined nine goals to Carlton duo Harry McKay and Charlie Curnow, face another huge task against the Lions' tall attackers Joe Daniher and Eric Hipwood.
But Simpkin backed fullback Aidan Corr and an undersized back-line to remain undaunted by the challenge.
"It's obviously tough, I think most weeks they're going to be undersized coming up against these tall guys," Simpkin told reporters.
"Our small defenders don't quite have that height, but the best thing about those guys is they will fight to the end, they are never going to give up.
"You don't have to worry too much about their effort, it's always going to be there."
Simpkin said North's collective resolve remained strong despite losses by 39, 26 and 59 points this season.
"We've had quite a tough start to the season," he said.
"We played the Giants who were in a prelim (preliminary final), Carlton played in a prelim, and obviously we have got the Lions tomorrow who played off in a grand final.
"The Lions, they will come out firing looking for their first win."Â
Brisbane made two changes, dropping Darcy Fort and Deven Robertson for Darcy Gardiner and James Tunstill.
The Kangaroos are without Callum Coleman-Jones (achilles) and left out both Charlie Lazzarro and three-game defender Toby Pink.
Charlie Comben, Liam Shiels and Hugh Greenwood have been recalled.
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