Yankees manager Joe Girardi said that a change was prompted after Chamberlain's effort on Tuesday against the Rangers, when the 23-year-old struggled on eight days' rest, allowing seven runs on nine hits in four innings.
Girardi said that he had been encouraged by Chamberlain's work in three starts out of the All-Star break, going 3-0 with a 0.83 ERA. But Chamberlain was 1-2 with a 8.55 ERA in the four starts that followed, allowing opponents to bat .321 against him.
"It looked like it was working great," Girardi said. "He came out of the break and was lights out. But we think that a change needed to be made."
"We tried it and it didn't work," Chamberlain said. "Now we're going to try this, and I think this is going to be great."
Girardi said the Yankees have not deviated from their innings limit for Chamberlain, who is scheduled to start on Sunday against the White Sox and every fifth game thereafter, weather permitting.
But while that innings limit was fixed, the rotation mapping had remained fluid. Girardi said that he discussed the situation with general manager Brian Cashman and pitching coach Dave Eiland this week, with Chamberlain being brought up to speed on Friday at Yankee Stadium.
"He's in the starting-pitcher mode in the sense that he's going to get the ball every fifth game," Girardi said. "As far as innings, there's going to be games that will be short. I will say that. He might not factor in a decision."
So while Chamberlain may begin September turning in efforts of less than five innings, Girardi said that it is crucial the righty becomes built back up for distance by month's end for the postseason, when the training wheels are removed, so to speak.
"We think it's important that, by the end of the month, he's able to throw 100-110 pitches," Girardi said.
That should not be a problem, as Chamberlain said that he feels as though he is in the best shape physically of his life, speaking to reporters on Friday only after being led through a grueling workout by teammate Andy Pettitte.
"It's going to help him, because he's going to be in a regular routine as far as being part of the rotation," Eiland said. "His in-between work and all the weight work he does between starts is going to be on a regular schedule, and not be erratic where he's throwing three or four sides between starts. He's going to stay on routine."
Despite that healthy state, allowing Chamberlain to make full starts on regular rest is not an option, Girardi said.
"I think if we were able to let him go the rest of the way, it's possible that he would end up at 180 innings," Girardi said. "For us, we feel that there's a danger at 180 innings. That's probably more than I've exposed about the innings limit at any point this year."
Having rosters expand to 40 players on Sept. 1 will help the Yankees in the early going, as they will have more available options to soak up innings in relief of Chamberlain's shortest efforts. Chamberlain has been receptive to the plans New York has created for him.
"This game is about adjustments," Chamberlain said. "It's going to be adjusted throughout the whole year. I'll never make excuses, but I haven't been good in my last three starts. I've got to do what's best for this team."
Chamberlain compared the eight days of rest to coming back disoriented from a long vacation. Instead of facing hitters, Chamberlain spent a day before his last start throwing pitches in a bullpen session with Mike Harkey standing in as a batter and Eiland calling balls and strikes.
"He got taken out of his routine," Eiland said. "You try and simulate his work between starts like he's facing hitters, but there's no substitute to actually facing hitters and getting reactions on swings. There's no pressure to make that big pitch when you're throwing on the side."
Chamberlain said that preparing to work every five days -- even if it is only for less than five innings -- would fit better, even if his preference might be to pitch nine innings every game.
"I'll never be OK as a competitor," Chamberlain said. "You want to pitch every out of every game. But I also understand that they care a lot about me, and that speaks a lot to this organization. It's frustrating to all of us at times, but we all know what's going to be best for this team."
Chamberlain said that Girardi joked that he was running out of erasers in revising all of his planning, but there have been multiple rules and regulations regarding the hurler since his arrival in August 2007. This is just one more chapter in the book.
"I've learned to be very patient over the three years that I've been here," Chamberlain said. "The Joba Rules are still going strong. I still see the T-shirts every once in a while. But it's better. It's going to make everything better in the long run."