Whiteside appeared in 12 games for the Giants last season and hit .091 in 11 at-bats. He has a career .215 batting average in 208 games with Baltimore (2005) and San Francisco (2009-12).
Toronto is now at full capacity on its 40-man roster. Unless the club makes another move in the near future, it will be forced to take a pass during Thursday's Rule 5 Draft.
The Blue Jays once again have four catchers on their roster. J.P. Arencibia is currently the starter, with veteran John Buck as the backup and top prospect Travis d'Arnaud waiting in the wings. Whiteside essentially replaces Bobby Wilson, who was non-tendered late Friday night.
Toronto's depth at the position could potentially set the table for a trade during this week's Winter Meetings. Several teams are in the market for a starting catcher and likely will attempt to make a run at either Arencibia or Buck.