Koenig (elbow) said his live bullpen session went well Tuesday and he expects to begin a rehab assignment with Triple-A Nashville on Friday, Adam McCalvy of MLB.com reports.
Koenig hit the 15-day injured list April 6 with a left elbow sprain and was diagnosed as having UCL damage. The southpaw was able to resume throwing April 28 and returned to mound work May 12. Given where he is in his rehab process, the reliever's return looks likely to come in early-to-mid June.