The Cowboys designated Harper (Achilles) to return from injured reserve Thursday, Todd Archer of ESPN.com reports.
Harper, who's been on injured reserve with an Achilles injury since Oct. 29, can now resume practicing ahead of Sunday's divisional-round matchup versus the 49ers. The rookie linebacker will have 21 days for a potential activation to Dallas' active roster, though he'd likely operate in a strict special-teams role off the bat.