Webster leapt off the ground and collected Simpkin's head with a hip-and-shoulder bump during the first quarter of the clash at RSEA Park on Sunday.
The Saints dominated early and resisted a second-half fightback as they squeezed out an 11.18 (84) to 10.5 (65) win in their final tune-up for the home-and-away season.
But Dougal Howard limped off late with a hamstring injury and the fall-out will likely include Webster being sent straight to the tribunal for a late bump that left Simpkin dazed after he kicked the ball into North's forward line.
The skipper has been ruled out for the rest of the match, following this high hit.— North Melbourne FC (@NMFCOfficial) #Kangas pic.twitter.com/dmAaZXAzJSMarch 3, 2024
Kangaroos players rushed to remonstrate with Webster and a melee spilled over the boundary line while Simpkin lay on the ground.
The 25-year-old was attended to by medical staff before being helped off the field and was soon ruled out of action for the rest of the match.
Simpkin suffered concussion twice last season but the Kangaroos are yet to confirm whether he was concussed from Webster's bump.
The incident came less than a week after Port Adelaide forward Sam Powell-Pepper was handed a four-match ban at the tribunal for a bump which concussed Adelaide's Mark Keane.
Collingwood great Nathan Buckley declared Webster's bump "at least twice as bad" as Powell-Pepper's and pondered whether it would result in a much larger suspension.
For mine this is one of the issues of hedging SPP's action at 4 weeks. Webster action was at least twice as bad in my view. Does that mean it's an 8 week penalty?— Nathan Buckley (@ncb_cfc) March 3, 2024
The first-quarter flashpoint occurred during a fast-paced opening as Max King's two early majors helped the Saints to a 13-point lead at quarter-time.
St Kilda dominated the second term but were wasteful, managing just 3.10 from 21 forward entries as the lead grew to 33 points by the main break.
North took advantage of a strong breeze in the third quarter, with Nick Larkey kicking two of their five unanswered goals as they cut the deficit to just three points by the final change.
Larkey's third major put the Kangaroos in front early in a hotly contested last quarter before St Kilda steadied.
King, Tim Membrey, Mitch Owens and Cooper Sharman kicked two goals each, while first-round draft pick Darcy Wilson (24), Nasaiah Wanganeen-Milera (29) and former Port Adelaide defender Riley Bonner (30) impressed.
North's No.4 draft pick Zane Duursma showcased his strong marking and kicked two goals, as did Cameron Zurhaar, while ex-Carlton playmaker Zac Fisher (36 disposals) and best-and-fairest winner Harry Sheezel (32) were busy.
Saints young gun Mattaes Phillipou sat out the second half as a precautionary measure with a sore hip.
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