Adam Schefter of ESPN passed along a statement from Coughlin after the announcement:
I met with [owners] John Mara and Steve Tisch this afternoon, and I informed them that it is in the best interest of the organization that I step down as head coach. I strongly believe the time is right for me and my family, and as I said, the Giants organization.
It has been an honor and a privilege to serve as head coach of the New York Football Giants. This is a not a sad occasion for me. I have spent 15 years with this organization as an assistant and head coach and was fortunate to be part of three Super Bowl winning teams. A Lombardi Trophy every five years is an achievement in which we all take great pride.
Obviously, the past three years have not been what any of us expect, and as head coach, I accept the responsibility for those seasons.
I think it has been evident these last 12 years here how much pride I take in representing this franchise. I am gratified and proud that we were able to deliver two more Lombardi trophies to the display case in our lobby during that time. That is a tribute to our players and staff, and it was truly fulfilling to be the leader of those teams.
I appreciate the support of John and his family and Steve and his family, and of Jerry Reese and his staff. I think our organization is a great representation of what I mean when I talk about 'team'.
Finally, I would be remiss if I did not thank my wife Judy and our four children and their spouses and our 11 (soon to be 12) grandchildren. None of this would have been possible without their unconditional love and support.
On Sunday, Coughlin thanked fans, as provided by Art Stapleton of the Record:
Art Stapleton @art_stapleton
Tom Coughlin says thanks to #Giants fans in today's editions of @TheRecordSports. A class act as always. @tcjayfund https://t.co/hPnnwTWKK11/10/2016, 2:23:25 PM
While Coughlin is out in New York, he is not retiring. Mike Garafolo of Fox Sports reported that, per a source, "if the right opportunity presents itself, he will coach again."
Mara told reporters on Jan. 5 that he asked Coughlin to remain with the organization "in some capacity," and the former head coach said he would consider doing so.
Coughlin's future has been a hotly debated topic among fans, and most signs pointed to his departure one way or the other.
Five postseasons in 12 years won't cut it, especially in a hyper-critical media market like New York.
The final nail in the coffin for Coughlin likely came after the lifeless 49-17 defeat at the hands of the Minnesota Vikings in Week 16. Pro Football Talk was surprised at the lack of effort from New York's players in that matchup:
Tom Coughlin told the Giants players not to think about his future? Based on how they played last night, they already aren't.12/28/2015, 10:24:03 PM
"If I was running a company and things weren't going the way that I wanted it to go, of course I would have to make changes," cornerback Prince Amukamara said after the Vikings loss, per Bill Pennington of the New York Times. "Whatever those changes are, I don't know."
The entire team didn't quit on Coughlin, but enough players did for it to be a problem. Once a coach has lost the locker room, there's no going back; a mutual separation is the only option.
In addition to the Giants' poor record, Odell Beckham Jr.'s one-game suspension only weakened Coughlin's job security. Many wondered why Coughlin didn't remove Beckham from the Giants' Week 15 loss to the Carolina Panthers when it was clear the star wideout wasn't in the right frame of mind.
Sporting News' Jesse Spector criticized how Coughlin handled the situation:
Jesse Spector 📎 @jessespector
Tom Coughlin, Mr. Discipline, everybody! https://t.co/IX7S4NXkb612/20/2015, 10:56:35 PM
ESPN's Antonio Pierce (via NFL on ESPN) also argued the coach hadn't done enough to hold Beckham accountable in the past:
NFL on ESPN @ESPNNFL
NFL LIVE's Antonio Pierce believes Giants coach Tom Coughlin has enabled Odell Beckham Jr. to do anything he wants. https://t.co/KyqaGPvIO712/22/2015, 9:39:30 PM
Coughlin alone isn't responsible for the the team's failure to post a winning record since 2012. Giants general manager Jerry Reese deserves a share of the blame, too. New York's draft history has been unimpressive lately, and the front office didn't do enough to improve the defense this past offseason.
Still, it was time to let Coughlin go.
New York doesn't have a Super Bowl window unless it makes sweeping changes and freshens things up. Thinking about the eventual succession plan from Eli Manning wouldn't be a bad idea, either, with the quarterback having turned 35 on Jan. 3.
Neither of those aims could be achieved with Coughlin still in the fold. The Giants may suffer in the short term as they transition to a new head coach, but his departure will benefit the franchise in the long run.