Manager Joe Girardi said on Monday that Chamberlain has stepped into the role for the time being. The right-hander was called upon for three outs in New York's 4-3 win over the Minnesota Twins on Monday, retiring all three batters he faced.
"We love the way he threw the ball in Spring Training," Girardi said. "Joba has the ability to get lefties out as well as righties."
Girardi said he altered his bullpen mix somewhat because left-hander Pedro Feliciano has been lost until at least later this month with a left rotator cuff strain. Boone Logan is the lone lefty, while Dave Robertson has been pushed back to the sixth inning by Chamberlain.
"That's the fun part of being in the bullpen -- you get a chance to do it every day," Chamberlain said. "It's one of those things where I feel very confident facing left-handers and right-handers."
In the seventh inning on Monday, Chamberlain got Jason Kubel to fly out, then induced groundouts from Danny Valencia and Alexi Casilla.
"To me, the thing that stands out is how well Joba threw the ball," Alex Rodriguez said. "He threw the ball with a lot of conviction, and it was predominantly fastballs in the 90s."