Air Carrier Captain reported during takeoff roll left engine torque did not rise resulting in the aircraft making a sharp left turn; the captain was able to regain control of the aircraft and departed safely.

Narrative

After loading at the cargo ramp; weather at destination dropped below minimums causing me to initiate a weather delay. My chief pilot asked me to taxi to our ramp instead of waiting on the cargo ramp. I did this single engine to conserve fuel since I knew weather was going to be an issue. During the reposition; I received a report that weather was now above minimums at destination; followed by a call from the boss telling me to go. I proceeded to our ramp; started the other engine; and called for a departure clearance. In getting out of routine; I failed to take the left engine off the start locks. On takeoff roll; left hand torque did not rise. I immediately recognized the propeller had not come off the start locks so I slowed down and applied reverse to release the start locks. During this maneuver my hand slipped off the nose wheel steering button allowing the nose wheel to caster freely resulting in a sharp left hand turn which caused the aircraft to depart centerline. I regained directional control; returned to runway centerline; ensured normal engine acceleration; and continued the takeoff with no further incident.