Jack Finley, Oskar Sundqvist and Nathan Walker were assigned to the Springfield Thunderbirds on Saturday.
With the moves, the Blues training camp roster is now at 25 players.
The team will have to reduce the roster to 23 active players by the NHL's deadline of Monday, Sept. 28 at 4 p.m. CT.
The regular season opens on Oct. 2 in Dallas, then continues with visits to Colorado (Oct. 3) and Chicago (Oct. 6). The home opener is set for Oct. 8 vs. San Jose at Enterprise Center. Tickets are available online at ticketmaster.com.
