Kieboom's absence from the lineup for Tuesday's game against Miami is due to a jammed thumb, Mark Zuckerman of MASNSports.com reports.
Kieboom is evidently not sitting due to the slump which has seen him hit .061/.205/.061 over his last nine games but is instead dealing with a minor injury. He'll be available off the bench, so he's unlikely to miss much more time. Jordy Mercer starts at third base.