The tight end will undergo back surgery on Friday for a herniated disc and be out at least several weeks, NFL Network Insider Ian Rapoport reported.
"We do not expect that he will be able to play for the remainder of the 2016 season, but will await the results of (Friday's) surgery before making a final determination," the statement said.
The Buffalo News' Vic Carucci first reported the news.
"It doesn't help losing great players," Brady told Jim Gray on the Westwood One Radio Network, "and to not have Gronk out there as one of our best players and most dependable, consistent players ... makes things challenging for us, but that's what the NFL season is about. It's about overcoming challenges, adversities."
While the team initially thought the tight end could return in short order, further examination revealed he needed surgery.
Although the injury likely won't stop the Pats (9-2) from making the playoffs, it's a severe blow to their Super Bowl chances if Gronk can't return in the postseason.
Friday's procedure marks the third on the 27-year-old's back, after surgeries in 2009 and 2013.
It's safe to start pondering whether Gronkowski's Hall of Fame-caliber career will be chronically marred by recurring injuries. The seventh-year pro had already missed 18 games (not including playoffs) in his career due to injury before the back injury.
2016: Hamstring, lung (3 games)
2015: Knee (1 game)
2013: Back, forearm, ACL/MCL, concussion (9 games)
2012: Hip, forearm (5 games)
The loss of Gronk is a severe blow to Brady. The Pats' offense becomes much less dynamic without the matchup nightmare, especially in the red zone.
With Gronk: 31.2 PPG, 391.9 total YPG, 279.2 pass YPG
Without Gronk: 26.9 PPG, 382.6 total YPG, 252.4 pass YPG
In his 86 games with Gronkowski, Brady has a 104.5 passer rating with a 65.5 completion percentage. Brady's numbers dip to 84.4 and 57.5 percent without Gronk.
Gronk's rare combination of size and athletic ability make him a demon for linebackers, safeties or cornerbacks in coverage. Since entering the league, Gronk leads the NFL in TD receptions with 68. Earlier this year he set the Patriots all-time touchdown record with 69.
In Gronk's absence Martellus Bennett is the logical next man up, but he's also dealing with ankle and shoulder injuries. Brady will also lean on improving rookie Malcolm Mitchell -- a receiver with hands the quarterback compared to Gronk's earlier this year. Backfield pass catchers Dion Lewis and James White could also see an increased role as Josh McDaniels attempts to diversify his offense after losing its biggest matchup.
Here is the complete statement on Gronkowski from the Patriots:
During the Seattle game on November 13, Rob sustained a hit to the chest that resulted in a pulmonary contusion to his lung. Rob was examined by several specialists at Massachusetts General Hospital as directed by the team, as well as an independent physician. He received medical clearance to return to play two weeks later for the New York Jets game on November 27. After a hit early in the Jets game, Rob began to experience significant back and leg pain. This injury forced him to leave the game and he did not return. With the help of the Patriots medical staff, along with the consultation of several medical experts, it has been determined that it is in Rob's best long-term interest to undergo surgery to address his lower back injury. Rob is expected to have surgery tomorrow. We do not expect that he will be able to play for the remainder of the 2016 season, but will await the results of tomorrow's surgery before making a final determination. Rob has always been one of our hardest workers and was voted captain for the leadership he provides on our team. We are deeply saddened any time a player is lost to injury. We are committed to assisting Rob throughout his recovery and look forward to his return to playing football for the New England Patriots.