Palacios (knee) was pulled off of his rehab assignment Wednesday after experiencing right hamstring tightness, MLB.com reports.
Palacios has appeared in only one game this season and has been sidelined since April 17. He appeared to be nearing a return but will now be pulled off his rehab assignment for the second time. The Rays do not have a timeline for Palacios' return, but he is set to undergo further evaluation.