"It's getting worse, not better," Hanigan said. "It's some sort of sprain in the ligament or capsule or something. It's lingering constantly, so I'm trying to calm it down."
Hanigan has been Bronson Arroyo's regular catcher the past four seasons. The last time Arroyo did not have Hanigan catching for him was Sept. 27, 2011, vs. the Mets. Hanigan was injured and Mesoraco caught the game as Arroyo allowed four runs and nine hits over eight innings.
On Saturday, Arroyo held the Marlins to just a pair of runs in eight innings.
Although nagged by the thumb since it was struck by a foul ball at St. Louis on April 9, Hanigan has struggled offensively. He entered the day batting .079 (3-for-38). A MRI exam taken on the thumb recently showed no serious damage.
Hanigan avoided speculation about whether he might need to go on the disabled list. Besides Hanigan and Mesoraco, the Reds do not have any other catchers on the 40-man roster. Veteran Corky Miller would be a logical choice to come up from Triple-A Louisville if there is a need.
"I don't know. We'll have to see what they want to do," Hanigan said. "I don't want to comment on that until I talk to them."
Mark Sheldon is a reporter for MLB.com. Read his blog, Mark My Word, and follow him on Twitter @m_sheldon. This story was not subject to the approval of Major League Baseball or its clubs.