Vic Carucci reported this first, and it was confirmed by Rapoport. Carucci said Gronk is expected to miss 8 weeks, which finishes his fantasy season, but leaves the door open for a possible late playoffs or Super Bowl return. Martellus Bennett is the obvious beneficiary, but he's dealing with ankle and shoulder injuries of his own. Julian Edelman, Chris Hogan, Malcom Mitchell and the pass-catching running backs will all try to pick up the slack.
Losing his top target is a big hit for Tom Brady, but Brady is averaging 23.7 fantasy points in two games without Gronk this season (vs NYJ and SF), on par with his numbers with Gronk.