OAKLAND, Calif. -- Sonny Gray's disappointing season got even worse Saturday.
Oakland's ace left after five innings with soreness in his right forearm, and Jake Arrieta pitched eight innings of three-hit ball to help the Chicago Cubs beat the Athletics 4-0.
Gray (5-11) felt soreness in his right extensor muscle while allowing two runs and five hits. The injury is the latest setback in a disastrous season for the 26-year-old right-hander, who's already been on the DL with a right shoulder injury.
Gray, a 2015 All-Star who last season finished third in AL Cy Young balloting, had the highest ERA in the majors (5.84) going into Saturday.
"He had really good stuff today, so it's unfortunate to hear that he's hurt because this is the best he's looked in a long time," A's catcher Stephen Vogt said.
Gray first felt the injury after striking out Dexter Fowler with a curveball in the top of the fourth.
"I was trying to go back out there for the sixth," Gray said. "I told them after the fourth I had a little bit of an issue come up and when I went back out for the fifth it kind of felt the same.
"They kind of decided to shut it down there. I lobbied to go back out there. It obviously wasn't going to happen."
The severity of the injury wasn't immediately known.
"Hopefully it's minor," manager Bob Melvin said.
"Looked like he was throwing the ball pretty well," he added. "He didn't come to me, he was trying to get some heat on it and go back out there. When he talked to the trainer about it, then we felt like we need to get him out of there."
Information from The Associated Press was used in this report.
Oakland's Sonny Gray leaves start with forearm soreness