The 26-year-old right-hander has struck out eight and is yet to allow a hit or walk in five innings over four rehab appearances since suffering an open dislocation of his right ankle in March. He also underwent Tommy John surgery last June.
Manager Joe Girardi said the Yankees still do not have an expectation of when he will return, but the plan is to continue to shorten Chamberlain's time between outings until he can pitch on consecutive days. Chamberlain began his rehab assignment July 10, and it can only last 30 days if there are no setbacks.
"We're encouraged," Girardi said, "and it seems like we're getting through this and it shouldn't be a real long time if everything goes according to plan."
Girardi said he would not hesitate to throw Chamberlain on consecutive days upon his return, but would more likely attempt to avoid situations where Chamberlain throws three times in four days.
Girardi would like to ease Chamberlain back into the bullpen, but the skipper trusts him against both right-handers and left-handers and said if he is throwing well and closer Rafael Soriano or setup man David Robertson need a day off, Chamberlain could see late-inning action.