Upshall, who joined the Blues as a free agent last summer, would have become an unrestricted free agent on July 1.
The Fort McMurray, Alberta native played in 70 games for the Blues last season, scoring six goals and eight assists (14 points) to go along with a plus-5 rating.
Overall, Upshall has played in 623 career regular season NHL games, posting 121 goals and 127 assists (248 points).
If not signed by July 1, David Backes, Troy Brouwer, Steve Ott and Kyle Brodziak will all become unrestricted free agents.