The move was announced Sunday.
Drouin was sent to Syracuse on a conditioning assignment Thursday after missing the preseason due to a broken right thumb. He had a goal and two assists in two games.
The third overall pick in the 2013 draft was one of junior hockey's top players the past two years, finishing with 29 goals and 108 points in 46 games last season for Halifax of the QMJHL.
The Lightning play the second of a five-game road trip Monday night against Edmonton.