"He hasn't pitched well. He needs to pitch better," GM Ruben Amaro Jr. said. "He can. Again, kids, man. When a guy doesn't have a whole lot of experience, you have to give them chances to find success."
But Amaro said he sees value in Rosenberg.
"He has good stuff," he said. "His location has been poor. He's getting whacked. But he has a good arm. He has to pitch better."
• Manager Ryne Sandberg has used John Mayberry Jr. as a defensive replacement for Ryan Howard at first base twice in eight days. It is a trend that could continue.
"He has not played well defensively," Amaro said of Howard. "He needs to be better. Pretty simple."
• Marlon Byrd took a seat Monday for Mayberry, who played right field. Byrd had played every inning of every game until Monday. He also had hit .217 (5-for-23) with one double, two RBIs, two walks and three strikeouts in his career against Dodgers left-hander Paul Maholm, while Mayberry hit .750 (3-for-4) with one double.
• Darin Ruf is starting to swing in the batting cage. He is on the disabled list with a strained left oblique.
"He's starting to progress," Amaro said. "I'm not sure when we'll get him into games yet."
• Right-hander Ethan Martin is on the DL with right shoulder inflammation. He is progressing.
"Right now he's trying to work on some of his mechanics," Amaro said.
• Right-hander Miguel Alfredo Gonzalez (right shoulder tendinitis) also is progressing. He has thrown off a mound a few times.
"Hopefully by the end of this month, they'll start throwing to hitters," Amaro said.
Todd Zolecki is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.