As a follow-up to this given I was so curious. I asked Baseball Prospectus the following question given the Cot's component of their website: "do you know the history of Free Agent signings where a 3+ year contract was extended after 1 season of said FA deal?" Their response, from Jeff Euston, is the following in its entirety: "This is exceedingly rare. Among active players, the only other case of this I can find is Glen Perkins, who also received an extension after one season of a free agent contract from Twins GM Terry Ryan. Absent an opt-out clause like the one in CC Sabathia's first Yankees contract, it's generally not done with free-agent contracts. The handful of other cases in which a player was extended with two or more years remaining were young players who had signed below market long-term deals before free agency, put up performances so strong they were still underpaid, then later signed an extension with the same club. A few of those examples are Miguel Cabrera (March 2008 and 2014), Ryan Braun (May 2008 and April 2011), Justin Verlander (February 2010 and March 2013), Evan Longoria (April 2008 and July 2013), Salvador Perez (February 2012 and March 2016) and Ryan Zimmerman (April 2009 and February 2012)." So realistically, and given Glen Perkins is the only other name they came up with, I can count the number of times this has happened on exactly one finger as lined up with my intuition. And Terry Ryan is literally the only GM to do this in modern times.