Coach Michael Voss will deliberately hold the two champions back early in the pre-season to ensure they are cherry ripe for round one next March.
Brown was a surprise attendee at Monday morning's first pre-season session at Coorparoo, less than 24 hours after his wife Kylie gave birth to a son, Jack William.
The 31-year-old captain did not participate in any of the running and left early.
Although Black completed the 2km time trial and a number of other drills, Voss said he would hold the pair back in the coming month.
He said Brown would be particularly quiet following his recent collision with a car while riding his bike.
"We've got to be mindful of the fact it was a big bang-up," Voss said.
"He'll take a pretty low-key approach until Christmas. It only takes a month or so to get him going so we won't see the big fella around until December, which will give him time to spend some time with Jack William Brown, who's the new father-son on the books.
"He's in good shape. We'll make sure we look after guys like Browny and Blacky coming into Christmas. It's more about mentally getting them in the right space because they come to hand (get fit) so quickly."
Black will be one of 18 Lions - entering their fifth year of service of longer - who will head to Arizona on Wednesday for a two-week altitude training camp.
Brown will stay in Brisbane.
"Both of them are going pretty well, so we'll hold them back," Voss said.
"We've encouraged them to stay away at this point in time. Blacky is going to Arizona, he loves it, so he'll be climbing Mt Humphreys in about three days time and be the first up.
"Our expectations with these guys is to keep it pretty low-key because they've had 15 pre-seasons, and it can be Groundhog Day after a while."
Voss was delighted with the general wellbeing of his squad on its first day back.
Reigning club champion Joel Patfull showed he was not resting on his stellar 2012 season, just being pipped by young midfielder Jack Crisp in the 2km time trial.
"These are important days because they signify what sort of physical gains you can make across the group," Voss said.
"There's always guys that can do better but there's some guys like Sam Docherty who looks like he's looked after himself.
"The one thing they've started to learn is … what it takes physically to play AFL. We've still got enormous growth in this group to come. "
Michael Whiting covers Brisbane Lions news for AFL.com.au. Follow him on Twitter: @AFL_mikewhiting
