The Blues assigned the 23-year-old Mojzis to AHL Peoria. He had one assist and 12 penalty minutes in seven games with the Canucks.
Weinrich, 39, joins fellow defenseman Chris Pronger and forwards Doug Weight and Mike Sillinger as veterans the Blues have dealt as part of a rebuilding effort. After 25 straight seasons of making the playoffs, St. Louis is near the bottom of the NHL standings and will almost certainly miss the postseason.
Weinrich had one goal and 16 assists, along with 44 penalty minutes, in 59 games for the Blues. He is in his 15th NHL season.