Yankees reliever Joba Chamberlain threw a bullpen session before Friday’s game with Kansas City, taking a positive step forward in his rehabilitation from a strained oblique muscle. Chamberlain is eligible to return on Monday. He may be ready right around then, barring a setback. Manager Joe Girardi indicated Chamberlain would work out of the bullpen again on Sunday. Then he would likely complete a brief rehabilitation assignment. “I wouldn’t imagine that he would need much,” Girardi said inside the visitors’ dugout at Kauffmann Stadium. “If he’s OK Sunday, I wouldn’t imagine he would need much more than that.” Chamberlain had pitched decently for the Yankees before getting injured. His ERA was 3.86, but he hadn’t allowed a run in his last eight appearances.