87 Rob Gronkowski, TE

Patriots tight end Rob Gronkowski underwent surgery on his back Tuesday, a procedure that the team expected him to have but not this late in the offseason.

ESPN reported Gronkowski's surgery was delayed because of the issues he had with his forearm earlier in the year. As a result it "does seem certain," according to NFL Insider Adam Schefter that Gronkowski will begin training camp on the Physically Unable to Perform (PUP) list.

Gronkowski could potentially stay on the PUP list through the first six weeks of the season. 

ESPN reports Rob Gronkowski will undergo back surgery on Tuesday. It will be his fifth surgery since last November but the first on his back. It is believed that Gronk will need 12 weeks to recover and rehabilitate. Gronkowski is also rehabbing from his latest forearm surgery, performed on May 21.

The Boston Herald reports that Patriots tight end Rob Gronkowski made a charity appearance Sunday at Gillette Stadium and still was wearing a protective sleeve on his left arm, a remnant from a fourth surgery that was needed to replace a plate to heal a broken bone in his forearm. He is also getting ready for a back procedure that will likely force him to miss regular-season games.