Hanrahan threw a 25-pitch bullpen session on Saturday, Tigers head athletic trainer Kevin Rand said.
The right-hander had his rehab process slowed last month to build up arm strength. It has been a reminder that while the recovery process for many pitchers has made elbow surgery look almost routine, it is anything but easy.
Hanrahan's contract has a $1 million base salary, with another $2 million in performance bonuses. Those bonuses depend at least in part on how many games he pitches as a Tiger.
Jason Beck is a reporter for MLB.com. Read Beck's Blog and follow him on Twitter @beckjason. Matt Slovin is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.