"It went really well," Masset said. "Lately, there's been some ups and downs. I had a setback about a week and a half ago. I started feeling some pain again. But we straightened some things out."
Masset missed all of 2012 with shoulder issues before having arthroscopic surgery in September. His throwing program was also halted at the end of Spring Training when he had a setback.
"That's been the recurring problem," Masset said. "I keep getting to the point where everything is going great and loose and I'm strong and flexible and my mobility is great. All of a sudden, I'll get a little pinch in the back of my shoulder. We've got to re-evaluate things to make sure everything is healing up OK.
"Right now, I'm cutting it loose pretty good. I'm fairly close to where I'm probably 100 percent fullspeed. But it goes from feeling completely normal to being my old self to what's going on here, and why all of a sudden is it acting up?"
Masset said he had thrown four bullpen sessions to date, and he hoped to get a few more so he could advance to face hitters in live batting practice. No target return date has been set.
"We could sure use him before the year is out," Reds manager Dusty Baker said.
That is Masset's wish as well. In the meantime, he will have to keep working his way back. His family has moved to the desert to be with him during his rehabilitation, and he watches Reds games from home each night.
"My hopes are to get back as soon as possible," Masset said. "We have to take the right steps in the right direction to put myself in the best situation to recover. As long as I'm feeling good, I will keep throwing. I can't really put a date on it. I just need to make sure I am healthy."
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.