Chamberlain is set to work off the Yankee Stadium mound before Saturday's game, and it is believed that the club could opt to activate him shortly after to begin working out of New York's bullpen.
"I feel fine," Chamberlain said. "Nothing's holding me back strength-wise. I've got one more test tomorrow and I think that hopefully will be the last one before I can get in a game."
The 22-year-old threw 45 pitches off a bullpen mound on Thursday, his most strenuous workout since he left an Aug. 4 start at Texas with what was diagnosed as right rotator cuff tendinitis.
Yankees manager Joe Girardi said that the outcome of Saturday's session could determine if the hard-throwing Chamberlain is prepared to rejoin the active roster.
"We're going to see how he does tomorrow facing the hitters," Girardi said. "The one thing that we've done is we have not rushed this and we have not tried to get ahead of ourselves. We won't do that. After tomorrow's performance, we'll make an evaluation to see if the next step is that he needs more time or we can activate him."
New York had transitioned Chamberlain into a starting pitcher beginning in June, but building him back into a starter would take more time, making a bullpen role likely. Chamberlain opened the season as the Yankees' eighth-inning setup man before joining the rotation, where he went 3-1 with a 2.76 ERA in 12 starts.
"We couldn't necessarily bring him back as a starter if we activated him right away, just because he's not built up," Girardi said. "I would have loved to have him back three weeks ago, but that's not the case. We had to deal with an injury and he's been feeling pretty good. We all feel good about that. We'll make a decision sometime this weekend."
Chamberlain is 4-3 with a 2.63 ERA in 32 games for the Yankees overall, walking 36 and striking out 104 in 89 innings. He said that watching from the sidelines as the club attempts to remain in contention for a playoff spot has been a trying experience.
"It's hard not being in battle with these guys every day," Chamberlain said. "You spend so much time being with them to get where you want to be. It's frustrating not being out there fighting and battling. I'm trying to get better and get back with them."
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.