This is a very surprising development. Ian Williams originally was slated to sign a 5-year deal, but that has changed to a 1-year deal due to an ankle injury.
The San Francisco 49ers reportedly agreed to terms on a 5-year contract extension with Ian Williams back on March 9, but the team has not announced the deal, and now it would seem we know why. Matt Maiocco initially reported Ian Williams's contract was revised to one year due to rehab from a procedure that was taking longer than planned. Then, Adam Schefter dropped the more significant information.