This from Cincinnati.com:
Guardado was out with forearm stiffness
HOUSTON -- Eddie Guardado was unavailable tonight due to forearm stiffness. It flared up on him in his last appearance Saturday, he tested it out this afternoon and didn't feel right, so they gave him a night off.
He said he'll be back and available tomorrow night.
"It was a little stiff the last outing I had, actually – just never got loose," he said. "To be honest with you, it takes a lot for me to be out of a game, I’ll tell you that. I’d rather be out there pitching than watching here, because your heart beats faster. They just gave me the day off today, which is fine, and tomorrow I’ll be ready to go out there."