He was available on a one-year deal for a reason. He had never shown anything close to what he did once he got here... he was a speed guy that had non-existent ballskills and had never developed. Hill is pretty much thr same guy minus the return ability.
He was available on a one year deal because Harbaugh buried him on the depth chart for an entire season instead of just letting him walk. He was never a sure thing, but his worth then is more than Hill's now.