The inexplicable ending of the AFC divisional-round playoff game two seasons ago - the 13 Seconds game against the Kansas City Chiefs that the Buffalo Bills somehow conspired to lose - seemed like the nadir of the Sean McDermott era for a franchise that was quite familiar with nadirs.But it turns out it might have been the peak.A 24-22 loss to the Denver Broncos in Buffalo on Monday Night Football leaves the Bills at 5-5, which is bad enough for a preseason Super Bowl contender. The schedule gets harder from here, and in an AFC with 11 teams at or above that mark, the Bills could already be doomed. At least they got the heartbreak out of the way early this time.It's not just that they lost on Monday night; this is a franchise with a lot of experience in gut-punch, prime-time defeats. It's that they were poised to win despite playing a largely disastrous game, one in which the offense remained stuck in its six-week funk and in which the defense kept them in it against a Broncos offense that was, weirdly, not trying all that hard to score points.It's that McDermott, having successfully called an all-out blitz to sack Denver quarterback Russell Wilson and push the Broncos out of field-goal range with 35 seconds left and no timeouts, called yet another all-out blitz. Given a second chance to get rid of the ball quickly and test an exposed Buffalo secondary, Wilson did precisely that, lofting a pass in the direction of Jerry Jeudy, who drew a pass-interference penalty that effectively won Denver the game by setting up a field-goal attempt.Even then, the Bills were almost gifted the win, as Denver rushed the kick with time winding down. Wil Lutz missed it, but the Bills had 12 men on the field, and Lutz hit the second attempt from 5 yards closer.On the sidelines, Buffalo quarterback Josh Allen was wide-eyed in shock, likely trying to process the stunning defeat while realizing that, as the Bills' quarterback, this might just be his fate now. Buffalo is where 99% win probabilities go to die. Rich Barnes / Getty ImagesAfter the playoff loss to the Chiefs in 2022, two things were evident. In Allen, the Bills finally had a quarterback who made them a title contender. His raw talent successfully honed, he had gone into Arrowhead Stadium and traded haymakers with Patrick Mahomes. But in McDermott, the Bills also had a head coach who had overseen an all-but-impossible collapse in those final 13 seconds and, notably, never really owned up to it.That was the nagging question, then: Sure, Allen was a thrilling player, but with McDermott in charge, was there a ceiling on how good this team could be? A big part of the head coach portfolio is late-game management, and McDermott hadn't proven he was good at it and got annoyed when he was asked about it.Eighteen months later, the Bills have thwacked their head on the McDermott ceiling. The combination of the late blitz call and the 12th-man penalties on Monday night is entirely on the coaching staff, especially when the Broncos had already executed a quick field goal at the end of the first half and were obviously setting themselves up to try the same thing. If McDermott is the kind of coach who benches a running back for fumbling the ball, which he did to James Cook in the first quarter, why not hold himself accountable for making avoidable mistakes?Perhaps that will come later. For now, Buffalo's response has been to fire offensive coordinator Ken Dorsey, who couldn't lift Allen and friends out of a funk that has lasted since the Week 4 win over the Miami Dolphins.Whether Dorsey deserves the bulk of the blame for that is questionable. While the offense has rarely been in rhythm, it has also been plagued by mistakes - drops, fumbles, interceptions - that can't be attributed to scheme or play calls. But it's also possible that the mistakes would clear up if the offense ever operated as it did in the glory days of 2021 under former coordinator Brian Daboll. Chicken? Egg? Unclear.The Bills were supposed to take advantage of a relatively easy early-season schedule to set themselves up for some tough tests on the way to the playoffs: Philadelphia, Kansas City, and Dallas all await in the coming month. Instead, the Bills lost games to Zach Wilson and Mac Jones, two quarterbacks who could be engaged in a season-long duel to see which is more inept. They almost lost at home to the New York Giants, who are 2-8 and gave up 89 points in two losses to the Dallas Cowboys. The Bills managed 14. And now, they've lost to a Broncos team that gave up 70 points to the Dolphins and seemed content to play 1970s football against Buffalo - all short throws and runs. And it worked. (Barely.)McDermott, the most successful coach the Bills have had since Marv Levy, needs to figure out how to turn this thing around. He started with Dorsey. It was always unlikely that he would start with himself.Scott Stinson is a former national sports columnist for Postmedia News.