The free-agent running back didn't hold back when discussing the move on Twitter:
Williams spent the first nine years of his career with the Panthers, overlapping with Gettleman for the last two.
The Panthers released Williams, their all-time leader in rushing yards and touchdowns, in March 2015.
During an appearance on the Know Them from Adam podcast last week, Williams said the Panthers were one of four teams he wouldn't play for next season, along with the Cleveland Browns, Jacksonville Jaguars and Dallas Cowboys.
"I had no problems with getting fired, but there are things that went on there that I didn't like—and I still don't like to this day," he told ESPN's Adam Schefter.
Interestingly, he had positive things to say immediately following his release in 2015.
"I don't feel bitter at all," Williams said at the time, per WBTV.
While he was upset no one from the organization came to his mother's funeral, he noted appreciation for Gettleman, who sent a thoughtful text.
"There's nothing that Coach Rivera and Dave Gettleman can do to me that will make me mad or make me hate them because in my darkest hour they were there for me."
His mindset has apparently changed, although the Panthers might not need the veteran running back after selecting Christian McCaffrey with the No. 8 pick in the 2017 NFL draft.