RBs are eminently replaceable in the NFL, that's the hard truth of it. Good ones come along every single year in all rounds of the draft. Murray played for 7 seasons, his skills are going to start eroding. He's smart to get out now.
I don’t blame him, tough position as you get older. I would say he’s still an average to average+ NFL back. I agree someone tries to unretire him but considering long term health risks I’d consider hanging it up as well.