Cooper's heel injury is believed to be muscular, rather than the ligament issue or plantar fasciitis that previously was reported, Todd Archer of ESPN.com reports.
Whatever the case, the Cowboys expect Cooper to resume practicing at some point next week. He'll likely be held out of preseason games, but coach Jason Garrett expects his No. 1 receiver to be fine for the regular-season opener. Cooper did some individual work -- including running routes -- earlier this week.