Gronk was reportedly good as gone in April until he threw a wrench in the Pats' plans.
According to ESPN, the New England Patriots and Detroit Lions were knee deep in trade discussion last April, and the centerpiece of the deal was none other than Rob Gronkowski. The information leak proposes that Rob Gronkowski's manifest destiny was the only thing holding back the transaction. Gronk apparently threatened retirement upon hearing of the forthcoming deal, which forced the Pats to end talks with the Lions.
If proven correct, the nixed deal could be considered a bit of an indignity towards the Lions' franchise. Rather than suit up for their team, Gronkowski would have forgone the rest of his NFL playing career. Gronk is evidently still in the prime years of said career, despite the injuries that have set him back. The sources who leaked the "nixed deal" assure ESPN that Gronk simply doesn't want to play anywhere other than New England, where he remains the focal point of a Tom Brady-led offense.
It is believed that Tom Brady encouraged Gronkowski's pressure tactic. It remains unclear why the Pats were considering dealing Gronk at this point of his career but in a way, it makes total sense. It would be wise to trade an injury prone tight-end before he reaches 30, as harsh as that may sound.
No man is bigger than Belichick's system, other than maybe Tom Brady, and I doubt be happy losing his favorite target, much like in 2006 when he coped with the loss of Deion Branch in a "non-banner year."