The only surprise is that it didn’t happen six days later.

Ever since his Bills endured a self-inflicted 34-31 overtime loss to the Dolphins on Saturday afternoon at New Era Field, Rex Ryan had officially become Dead Coach Walking.

And, at lunchtime Tuesday, owners Terry and Kim Pegula made it official, a ninth coach, at least, would be offered the opportunity to end Buffalo’s now-17-year  playoff drought.

With Ryan fired, but walking away with a $16.5 million severance for the three seasons, plus one game, he didn’t coach, offensive coordinator Anthony Lynn takes over as Buffalo’s boss for the season finale Sunday against the Jets at the Meadowlands.

But for many in Bills’ Nation, the Pegulas only did half the job.

Clearly, Rex deserved to be axed.

His record wasn’t all that bad … 15-16 with Buffalo. But add his last four years with the Jets, and he’s 41-54 the past six seasons with no playoff appearances.

But it wasn’t his record with the Bills that got Ryan canned – after all, his winning percentage was better than any Buffalo coach since the no-playoff streak started, other than Wade Phillips, 8-8 in 2000 – but rather his failed promises.

The key one, of course, was the inability to produce a postseason appearance in two tries.

But, almost equally important, was the expectations he set for his defense.

On the night of his introductory press conference, Ryan alluded to former defensive coordinator Jim Schwartz’s defense, ranked fourth in the NFL in fewest yards surrendered the previous year, and called it disappointing.

Armed with a glowing defensive reputation, Rex maintained his goal was to be No. 1.

For the record, his defense ranked 19th last season and is in exactly the same place this trip, heading into Sunday’s finale. In two years, Ryan’s defenders totaled a mere 59 sacks. Schwartz’s crew had a league-leading 54 in 2014 and a franchise-record 57 the year before.

There’s no small irony that in Ryan’s final game coaching the Bills, his offense put up an all-time team-best 589 yards and the unit that ultimately led to his firing was his beloved defense.

Facing 4th-and-2 at Buffalo’s 41 in overtime and needing a win to stay alive in the playoff hunt, rather than going for the first down with an offense Miami couldn’t stop, Ryan elected to punt. He assumed his ‘D,’ which would give up 494 yards on the day, could hold, get the ball back and position the Bills to win the game.

That delusion lasted only one play when, on first down, Jay Ajayi, en route to his second 200-yard game against Buffalo this season, roared 57 yards putting the Dolphins in immediate position for the game-winning field goal.

Oh, by the way, the Bills had only 10 players on the field for Ajayi’s run, the same number defending against Andy Franks’ 55-yard game-tying field goal at the end of regulation.

Indeed, on that kick, Ryan also failed to get the timeout he swears he called and didn’t have his kick-block unit on the field.

Rex clearly  has never been one for details, but those are the difference between being a great coach and a mediocre one.

Sadly, his defensive reputation is a product of a bygone era and that exposed his reluctance to embrace the little things.

That’s why, his next job likely won’t be as a coach. Instead he’ll end up as a TV commentator where his outsized personality, charismatic bearing and unfiltered bluster will be a perfect fit.

Meanwhile, Lynn ends a bizarre season where he started as running backs coach, was promoted to offensive coordinator when Ryan fired Greg Roman two games in and ended up as head coach, if only for one game.

Clearly Buffalo’s offense improved when he took it over.

But he also takes some blame for Ryan not even being allowed to finish the season.

On the Bills’ first possession in overtime, when a touchdown would have won the game, Buffalo drove to Miami’s 19, facing 2nd-and-12.

Lynn called an end-around … which was fine.

However, carrying the ball was downside-of-his-career Reggie Bush. Coming in, all the 31-year-old running back had done was collect $1.5 million in salary and rush 11 times for a mere five yards.

Almost predictably, Bush was thrown for an 8-yard loss, setting up Dan Carpenter’s missed 46-yard field goal that could have been a game-winner.

Hopefully the decision was an aberration and that Lynn, as head coach, will be more realistic about his personnel groupings.

And finally there’s general manager Doug Whaley who, incredibly, emerges unscathed yet again.

Apparently the Pegulas believed him when he said he had supplied Ryan with “superior” talent. After all, he’s given credit for all the successful personnel decisions while his predecessor, Buddy Nix, gets the blame for the failures.

Worse, the owners doubled down on the safety of Whaley’s job by assigning him to lead the coaching search.

In effect, they hired Bernie Madoff to be a Chief Financial Officer.

And, thus, there’s one guarantee, the Bills won’t be getting a name coach.

No high-profile candidate would take the job without Bill Belichickesque power. And, if such a coach was hired, Whaley would figure to be one of the first to go … so he’s not hiring one.

As it is, the only reason he survived, and possibly even current managing partner and president Rus Brandon, is that Bill Polian turned down a job as Buffalo’s football guru two years ago.

Now Brandon is part of management in the Pegula empire, with both the Bills and Sabres and completely safe. Meanwhile, Whaley is in charge of finding the next coach.

But if I was the Pegulas, I’d trust him about as far as you can shot put an elephant.

It would be hard not to be suspicious when three “NFL Insiders” with national stages report that Ryan will be fired — the first coming  with four games to play.

And the only clue needed was the part about his being supplied with “superior” talent.

It’s a self-serving statement that would only come from Whaley or somebody who works for him and for no reason other than to save a job … or jobs.

No matter who, in Whaley’s personnel department, was the leak … it’s a show of profound disloyalty to the organization.

Instead, the GM survives again and now will choose the next coach to throw under the bus.

(Chuck Pollock, the Times Herald sports editor, can be reached at cpollock@oleantimesherald.com)