Speaking to reporters Wednesday (via Ed Bouchette of the Pittsburgh Post-Gazette), Tomlin said he has "no idea" when the NFL will clear Bryant to practice.
After being suspended for the 2016 season for violating the NFL's substance abuse policy, Bryant received a conditional reinstatement from the league in April.
However, per the NFL's official statement, Bryant would only be allowed to take part in all preseason activities "once arrangements have been confirmed regarding Bryant's clinical resources in Pittsburgh."
Steelers general manager Kevin Colbert said in a statement on July 27 the NFL informed the team Bryant was "still in the process of being fully reinstated" and unable to participate in practice or preseason games.
A fourth-round pick out of Clemson in 2014, Bryant showed tremendous potential in his first two seasons. The 25-year-old recorded 76 receptions for 1,314 yards and 14 touchdowns in 21 games in 2014 and 2015.