New England Patriots tight end Rob Gronkowski announced his retirement from the NFL Sunday on Instagram, saying he's "so grateful" for the time he spent on the team. Gronkowski, 29, played nine seasons with the Patriots, and thanked his teammates, fans, Patriots owner Robert Kraft, and Coach Bill Belichick for their support. Quarterback Tom Brady praised Gronkowski on Instagram, saying it was an "honor and privilege" to play with him. Gronkowski played 115 regular season games, with 521 receptions for 17,861 yards, a record for a tight end.

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