Hudson became a free agent when the D-backs declined to tender him a contract earlier this month. Hudson was eligible for salary arbitration and the D-backs were not willing to risk going to a hearing and seeing him get a raise after not being able to pitch since June 2012 due to an elbow injury.
Hudson made just nine starts in 2012 before having Tommy John surgery. In June, just weeks before he was set to return, he reinjured his elbow during a Minor League rehab start and had to have a second Tommy John surgery.
Hudson is likely to miss most, if not all, of 2014, and when he does come back it will likely be in a relief role.
Blanco, 42, will battle Tuffy Gosewisch for the backup catching role to Miguel Montero.
This will be Blanco's second stint with the D-backs, having played for Arizona in 2011 and '12, during which he had an OPS of .730.
Blanco, who has played for 11 different teams over 16 big league seasons, was with the Blue Jays and Mariners in 2013.
Steve Gilbert is a reporter for MLB.com. Read his blog, Inside the D-backs, and follow him on Twitter @SteveGilbertMLB. This story was not subject to the approval of Major League Baseball or its clubs.