Melvin said Hill was "a little bit sore" Monday, after departing Sunday's win against the Tigers in the seventh inning with the injury, "but we're not ruling out his next start yet."
"We'll take it day to day," Melvin said. "We'll probably have more news in the next coming days. He'll probably have an extra day regardless, but we could potentially skip him even one more [day] if we have to."
Hill threw 101 pitches on Sunday, fanning nine in 6 1/3 innings en route to his team-leading eighth win of the season. His 2.25 ERA ranks second in the American League to Chicago starter Jose Quintana's 2.13 mark.
Jane Lee has covered the A's for MLB.com since 2010. This story was not subject to the approval of Major League Baseball or its clubs.