There is ongoing speculation about Thomas, who is returning from an ankle injury and is yet to resume full training.
Coach Nathan Buckley said he had not ruled out Thomas from the round one match on March 31 against North Melbourne, but wouldn't risk the 25-year-old so early in the season.
"We're not going to push a bloke to play round one when it's going to put undue risk on him to re-injure [the ankle], and then you lose him for another month," Buckley said.
"We'll make the decision based on how well he trains between now and when he comes back and when we pull the trigger on him."
Thomas, Luke Ball, Alex Fasolo, Tyson Goldsack, Alan Toovey and Lachlan Keeffe have all had off-season injury issues.
Toovey and Fasolo could return to the side for next week's second round NAB Cup match against West Coast in WA.
Ball, whose season last year was ruined by a knee reconstruction, is slightly ahead of Thomas in his training.
"Luke could drop into full training at any stage in the next week and Dale is probably a week away from doing warm-up and full training in a couple of weeks," Buckley said.
"If 'Daisy' full trains in a week's time, we're still a month out from round one.
"If he was able to achieve that, he'd be around the mark for round one start."
One player who has had no issues with pre-season training is Brownlow Medallist Dane Swan.
The Magpies banned Swan for two games late last season for breaking a club alcohol ban ahead of the finals.
The Magpies have been rapt not only with Swan's pre-season form, but also his attitude.
"He's invested, he's showing a real care for his team-mates and the environment that he's operating in," Buckley said.
"That can ebb and flow in individuals, as it can in teams.
"But we feel like we're in good shape at the moment."
