Boxberger (back) was able to throw a pain-free bullpen session Sunday morning but is being sent back to High-A Charlotte for one more rehab outing, Roger Mooney of the Tampa Bay Times reports.
That appearance is scheduled to take place on Tuesday, after which the Rays will presumably activate Boxberger. Residual soreness after a Wednesday appearance with Triple-A Durham put a wrench into the plans to activate the veteran reliever at some point during the just-concluded weekend series versus the Orioles. However, with Sunday's bullpen going well, it appears Boxberger just needs to come out of Tuesday's outing setback-free to make his long-awaited 2017 big-league debut.