"Where he is right now, it might be another day or two before he picks it up again," Roberts told reporters.
The ace left-hander had announced on Friday that he was taking a step back from throwing, but didn't provide a specific reason. On Sunday, Roberts told reporters it was because of inflammation in Kershaw's throwing shoulder. He also said that Kershaw would play catch on Monday, but didn't specify how much he'd throw or at what distance he would throw from.
Robert said the results of Monday's session were concerning.
"It's not ideal," he said. "You're hoping when he picks up a ball that he comes out of it feeling better. So obviously it's not ideal. But we'll deal with whatever comes our way."
Roberts said there were still no plans for testing.
"We'll get together with the training staff and come up with a course of action for Clayton," he said. "But right now, we don't have an MRI scheduled."
Kershaw, 30, had a 2.73 ERA and a 1.04 WHIP last season. But his fastball velocity dropped to the low 90s, and his slider began to take on the characteristics of a cutter, giving Kershaw little differentiation outside of the rare times he threw his curveball. It prompted the lowest strikeout rate (8.6) and highest hit rate (7.8) since his rookie season in 2008.
The day he signed a three-year extension to remain with the Dodgers in early November -- a deal that basically tacked on an extra season to the contract he had opted out of -- Kershaw expressed his desire to "prove a lot of people wrong" and tap back into some of his velocity.
The three-time Cy Young Award winner then spent most of the offseason in Dallas trying to increase his flexibility and realign his delivery. He was noticeably less bullish when speaking to reporters about his previous desire to add velocity at the onset of camp, saying, "I think I was just fired up. I guess it just sounded good."
Information from ESPN's Alden Gonzalez was used in this report.