The 22-year-old Sobotka finished his third NHL season with 4 goals and 10 points in 61 regular-season games. He added two assists while playing in all 13 postseason games for the Bruins. In 134 career games, Sobotka has recorded 6 goals and 22 points.
Warsofsky, 20, registered 12 goals and 11 assists this past season for Boston University as a sophomore. He is a former member of the U.S. National Team Development Program and was a fourth-round pick of the Blues in the 2008 Entry Draft.