Weightman missed the pre-season clash with the Kangaroos due to groin soreness and the Bulldogs want to take a careful approach with the 22-year-old, who booted 36 goals last season.
No timeline has been set for his return, but he'll definitely miss Saturday's clash with Melbourne at the MCG.
"After having a really solid pre-season Cody experienced some groin muscle overload two to three weeks ago," Bulldogs head of sports medicine Chris Bell told the club's website.
"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."
Utility Dom Bedendo is suffering a similar injury and will be assessed in the coming week.
Small forward Arthur Jones, who was on track to make his AFL debut on Saturday, will now also miss the opening rounds of the season after suffering a groin injury late last week.
Defender Ryan Gardner is recovering well from elbow surgery and is on track to return within the next month.
"Gardner had a fall during a football session and cracked a bone in his elbow," Bell said.
"We decided that surgical management would accelerate his recovery. This surgery was successfully completed a couple of weeks ago.
"He will remain in a brace for another week and we expect to see Ryan back playing footy in the next 3-4 weeks."
Laith Vandermeer (cracked fibula) is slated to return in round five or six, while former Hawk Tim O'Brien (hamstring) and Roarke Smith (foot) are expected to be available a month into the season.
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