"It's a lot better today," Hamilton said. "I took the off-day yesterday to see the doctor, and everything's fine. Today, it's more of my decision if I could play or not."
In the sixth inning Saturday after he caught Paul Goldschmidt's deep drive, Hamilton didn't feel right after he made a long throw to third base as A.J. Pollock advanced on the out.
"It happened and it went away and I kept playing the game," Hamilton said. "And then the next day I was throwing the ball to bases in [batting practice] and I felt the same thing, but a lot more sharper pain and that's when I told [the club]."
Reds manager Bryan Price wanted to be cautious with Hamilton's arm and kept him out of Sunday's game.
"Our concern was getting worse if he has to throw from the outfield in Arizona," Price said. "Knowing we had a day off on Monday, it gave him two straight days off for him to get some of the soreness and swelling out."
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.