Reid hurt his left quad at training on Friday, meaning he has missed what would have been his second VFL game back from the calf injury he sustained in the pre-season.
The Magpies believe Reid could miss up to four weeks but Larkins believes it could be longer, given the premiership Pie's history with the injury.
"We'd normally put a four-to-six week timeframe on that, [but] he's had problems before so a recurrence of the same injury usually adds a bit more time again, because it is a weak spot," Larkins told AFL.com.au.
"The reason you do them is because you've done them before, so the biggest risk that you've got about doing any soft tissue injury is having had one before – it doesn't matter if it's calf, hamstring or a quad."
Larkins said it was a "standard" sort of quad injury, which has affected Reid's kicking leg.
The 25-year-old suffered the injury twice in the first half of the 2012 season and missed a total of five senior games.
His younger brother Sam missed 16 games for the Sydney Swans last year with a similar complaint.
Larkins said given Reid's history and lack of conditioning due to the pre-season calf injury, the Pies might not have him available until two or three weeks out from the finals.
"He hasn't played a game this year and he's had problems in the pre-season leading into his preparation," Larkins said.
"Here we are heading into round 14 and if he's looking at six weeks it may even be round 20 before he gets back to play.
"In maybe five or six weeks' time he might run 50 or 60 per cent of a game at VFL level.
"He's such a talented player that given that he gets through at VFL level, you think they'd put him back in pretty quickly, but you wouldn't think he's going to get back much before round 20.
"Often we see a player coming back and they say he needs a few games under his belt, we've even seen guys come back at VFL level like Chris Judd because you just need to get games.
"With Ben, you'd expect he'll play in Collingwood VFL once they're happy for him to be exposed to competitive match stuff, and that certainly wouldn't be in the next month I wouldn't expect.
"He's having a horrible season. He'll be needing lots of support."