Run is the operative word here.
Prior to Wednesday night, Barbosa had been averaging just 11 minutes per game. He got extra run against the Utah Jazz after Rajon Rondo's injury but has been minimally used in most games thus far.
The Celtics have been playing like they started the season trudging through mud. The bench players stumbled out of the gate and have been struggling to find their rhythm. Even Paul Pierce is shooting at the lowest percentage of his career.
Barbosa is the most recent addition to the Celtics roster and hasn't had as much time to assimilate into the system. Therefore it makes sense to use him sparingly this early in the season.
However, with everything he has shown and everything the team around him has shown, it is time to get the reserve guard in there for more minutes.