Over 46 games with the Mud Hens in 2014, Mercedes went 0-3 with three saves and a 4.92 ERA. Mercedes signed as an amateur free agent with Detroit in 2008.
The Tigers' 40-man roster remains at 40.
Joey Nowak is a reporter for MLB.com. Follow him on Twitter at @joeynowak. This story was not subject to the approval of Major League Baseball or its clubs.