Weightman has missed a portion of the Bulldogs' pre-season program due to the injury, which will now see the 22-year-old sidelined for the start of the home and away season.
The Dogs confirmed on Tuesday that Weightman won't face the Demons as the clubs take a cautious approach to his recovery.
“After having a really solid pre-season, Cody experienced some groin muscle overload two to three weeks ago,” Head of Sports Medicine Chris Bell said in a club statement.
“These injuries can be notoriously volatile and persistent, so to make sure we prepare him for the long season ahead, we will need to be patient to wait for these overload symptoms to settle down.”
“We will look to confirm Cody's return to playing plan when he is symptom free.”
Weightman's potential replacement, uncapped forward Arthur Jones, has also been ruled out of the Dogs' season opener after sustaining a groin injury of his own.
Jones, a Western Australian product in his second season at the Kennel, was seen as a live chance to earn his debut in Round 1, however, will now likely require further time to recover before his first senior game.
“This won't keep Arthur out for long, we are expecting him to be putting his hand up for selection in the first few rounds of the season.”
The Bulldogs are already without Ryan Gardner (elbow, 3-4 weeks), Tim O'Brien (hamstring, 4-5 weeks), Laitham Vandermeer (leg, 4-6 weeks), Roarke Smith (foot, 4-6 weeks) and Dom Bedendo (groin, TBC) for Round 1.
“Dayne is training really well and has made significant progress, but we need to ensure he has the opportunity to get more training volume under his belt,” Lions High Performance Manager Damien Austin said.
“The priority is to have him not only 100% ready to play but 100% ready to continue to play once his season gets underway.”
Zorko, Ah Chee and Gardiner could be in the mix to face Melbourne in Round 2 should they be deemed fit.