"He was in the bullpen, and it bothered him some getting down," A's manager Bob Melvin said. "I don't think his mobility was all there. Hopefully, with another day, he'll be able to catch tomorrow."
Jaso is batting .279 when catching and has a .195 average as the DH this season.
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. Teddy Cahill is a reporter for MLB.com. Follow him on Twitter at @tedcahill. This story was not subject to the approval of Major League Baseball or its clubs.