Manager Mark Kotsay said after Saturday's game against the Mariners that Jump has a shoulder impingement and will be re-evaluated Sunday, Theo DeRosa of MLB.com reports.
The left-hander felt some tightness while throwing in the bullpen prior to Saturday's start, but he pitched through it and was dealt his 11th loss of the campaign after giving up five runs across two innings. The A's figure to be cautious with Jump down the stretch as his rookie campaign nears the finish line.