Chamberlain was placed on the 15-day disabled list Wednesday due to rotator cuff tendinitis in his pitching shoulder. The right-hander saw Dr. James Andrews on Wednesday, one day after an MRI on the rookie's ailing shoulder.
"I'll be throwing in a week. I'll probably throw the beginning of next week," Chamberlain said Friday when he arrived at the Yankees' spring training complex. "Everything feels fine now."
The 22-year-old was removed from Monday night's start against Texas in the fifth inning with stiffness in his shoulder. He never thought the problem was serious.
"No. Not at all," Chamberlain said. "It would have been different if I wasn't still throwing 99 [mph]. It was a different feeling that I never had, so I just wanted to make sure."
When asked if he would be ready to start again for the Yankees by Sept. 1, Chamberlain said "I'll throw way before that in a game."
Chamberlain is 4-3 with a 2.63 ERA in 12 starts and 20 relief appearances.
Also, left fielder-designated hitter Hideki Matsui took a step forward in his rehab program for a sore left knee, reporting no problems on Friday, one day after starting a running program.
"The knee was fine, so I'm happy about that," Matsui said through a translator.
Matsui decided not to undergo surgery last month in hopes of playing again this season.
"The fact that the activities I had yesterday and the way the knee responded today, honestly I do feel positive in the sense that we're progressing forward," Matsui said.
Matsui was unable to work out on the field Friday due to rain. He did ride a stationary bike and took 54 swings during a hitting session in an indoor cage.