The right-handed reliever -- placed on the 15-day disabled list on June 13 with a strained upper back -- was scheduled on Friday to throw his second bullpen since suffering the injury but wasn't able to.
"He's still having some symptoms, even though they're minor from where they might have been 10 days ago," manager Mike Scioscia said. "But his progress has been slow."
Rodney, who started the season as the Halos' closer before rookie Jordan Walden took over, hasn't appeared in a game since June 8 against Tampa Bay. He's recorded a 4.09 ERA in 22 innings.