Manager Bud Black said Ross -- who was to start on Thursday against the Phillies -- has a combination of soreness and fatigue in his right arm. On Monday, Black told reporters Ross wouldn't make his next start.
Ross, who would have been in line to make three more starts had he stayed on schedule, will now rest and get treatment for a period of three or four days, Black said, before the team decides if or when he will pitch again.
"The next three to four days are critical in how he responds to treatment," Black said. "We're going to see how he reacts. There's no set time for him to get back on the mound."
In his past two starts, Ross has surrendered seven earned runs, 12 hits, six walks and has struck out 11 over 8 2/3 innings.
Ross is up to a career-high 195 2/3 innings pitched, 44 1/3 beyond his career high from 2012 (73 1/3 innings pitched with Oakland, 78 1/3 innings pitched for Triple-A Sacramento). His 31 starts were tied for the NL lead on Monday.
Robbie Erlin will start on Thursday against the Phillies, his first start with the team since May 17.
"This is an opportunity for Robbie to show what he can do against a Major League lineup," Black said.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.