"He's scored in the League recently, he's 26 years old, a player obviously we control for a year and would like to sign long term," said Blues General Manager Doug Armstrong after acquiring Buchnevich.
"He's the right age group for us with what we're trying to accomplish. A very good penalty killer, too."
Buchnevich, who spent his entire five-year career in New York, recorded 195 points including 79 goals and 116 assists and 112 penalty minutes in 301 regular-season games for the Rangers.
The Rangers acquired Sammy Blais and a second-round pick in the 2022 NHL Draft in the deal.