Kieboom said Sunday he is expected to require 4-to-6 weeks to recover from the flexor mass strain near his right elbow, Mark Zuckerman of MASNSports.com reports.
Kieboom has been shut down from baseball activities and is scheduled to undergo testing once the swelling has subsided later this week to rule out a potential UCL tear, which would be a much more significant injury. Either way, the 24-year-old is poised to begin the campaign on the injured list. Maikel Franco, a non-roster invitee, is now the likely favorite to open the season at third base for Washington, though utility players Ehire Adrianza and Richard Urena could also be considered.