Right-handed starter Brandon McCarthy (3-0, 5.87 ERA) is out for the season because of a torn ulnar collateral ligament, and he's likely headed for Tommy John surgery.
"Not very good news," Mattingly said at Dodger Stadium before his team played the Giants in the first game of a three-game series. "Brandon being out for the year is different than someone who's going to be on the DL for a couple weeks, then coming back."
Mattingly said he had expected to hear that tendinitis would shelve McCarthy, 31, for a while. The pitcher had told him what he felt was something that he'd had before and had gone away with rest and treatment.
McCarthy said, in a dugout interview, that Tommy John surgery was not yet a certainty, but he seemed headed that way.
"I don't want to stretch it out for several months and waste everyone's time," he said. "If this is what we need to get done, we're going to get it done and done soon."
McCarthy said the test results were a shock to him. Dodgers president of baseball operations Andrew Friedman said much the same thing.
"He never had had an elbow injury, so this falls into 'This happening to anyone' category," Friedman said. "His elbow looked healthy [in an MRI before signing] and it looked like a healthy elbow. This happens to pitchers. They get hurt and you have to act accordingly.
"Immediately my thoughts went to Brandon. Obviously it's a really difficult place to be for a competitor, to be out for a year. We told him we will stand behind him and get though this. So my immediate thoughts went to Brandon, then took a deep breath and try to figure out where we go from here."
The Dodgers, who are still waiting for left-hander Hyun-Jin Ryu (left shoulder impingement) to join the rotation, and right-hander Kenley Jansen (left foot surgery) to reclaim his closer's role, are now scrambling with McCarthy down, too. The veteran had struck out 29 and walked just four in 23 innings in his first season with the Dodgers.
"Scott [Baker] will stay here for now," Mattingly said. "We've already seen a number of guys in the fifth spot, and we have guys who have thrown the ball well.
"We still feel good about our club. Someone just has to step forward, and pitch well."
Left-hander Adam Liberatore was recalled from Triple-A Oklahoma City to take McCarthy's roster spot. Liberatore, 27, was with the Dodgers from April 17-21 and made three scoreless relief appearances in that span. He worked 4 1/3 innings, allowing one hit while striking out four. In three games for Oklahoma City, Liberatore allowed one run on three hits and struck out five in three innings.