Tiedemann (elbow) threw a live batting practice session Friday and could begin a rehab assignment this week, Shi Davidi of Sportsnet.ca reports.
The 21-year-old lefty last pitched April 11 for Triple-A Buffalo before being shut down with what was diagnosed as ulnar nerve inflammation in his elbow, but he's close to resuming game action. Tiedemann will likely begin his rehab stint in the Florida Complex League or with Single-A Dunedin, and he could rejoin the Buffalo rotation by the end of June. If Tiedemann can manage to stay healthy, he remains a candidate to bolster the major-league staff in the second half.