Strasburg (back) threw a bullpen session Thursday, Chelsea Janes of the Washington Post reports.
Strasburg was also able to throw a bullpen session Tuesday and is eligible to come off the disabled list as early as Friday. Despite that, manager Dusty Baker indicated he was not overly optimistic his ace would be able to return in time to make a start over the weekend. For the time being, the Nationals are listing Sunday's starter as TBA, so there figures to be a further update prior to that day's tilt.