"I think it's gone," Janssen said. "I guess you never know. But I do think it was one of the those things that once you got past a certain stage in it, I think it just becomes something you've done your whole life."
Nationals manager Matt Williams said Janssen will get a couple of days off after his first rehab outing before pitching again. The club would like him to pitch in back-to-back games before returning to the Majors.
Janssen compared where he is at now to the point when games begin during a normal Spring Training. Therefore, he continues to work on building arm strength and wants his velocity to "pick up a couple ticks," and for his breaking pitches to get sharper.
Janssen doesn't rely on velocity -- his fastball averaged 89.7 mph last season -- and Williams isn't worried about it.
"That's part of the progression," Williams said. "Once you had an issue and get shut down a while, you have to build strength, and that strength comes from competitive innings."
Janssen, who signed a one-year deal with the Nats in February, was slated to be the setup man for closer Drew Storen, after Tyler Clippard was traded to Oakland. Things have not gone as planned for the 33-year-old, but he is hoping he can return to his new club soon.
"It's frustrating when you've worked the whole offseason to have a healthy Spring Training and to have a healthy season," Janssen said. "I definitely didn't draw it up to make it look like this. So that's disappointing. It's disappointing to not be here helping. But you've just got to deal with it, get through it, get back as fast as you can and try to help this team win some games."
Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.