What had been suggested over four games and nine days was confirmed in an outrageous Game 5: The sub-.500 Atlanta Hawks are better than the East’s No. 1 seed. Should they close this out Thursday at Philips Arena — and they should — this will be viewed as one of the NBA’s monumental first-round upsets. On the court, this is no upset.

This is a case of scheme and execution wrong-footing an opponent that has spent two months playing its way down to mediocrity, and the Indiana Pacers’ slide is almost complete. A smart team is cutting a befuddled one to ribbons and then, just for effect, tying those ribbons into pretty red bows.

The Hawks won Game 5 on Monday and No. 8 seeds aren’t supposed to go on the road in a tied series and win, let alone win by 10 points after leading by 30. But really, what was so hard to believe? The Hawks have beaten Indiana three times in Bankers Life Fieldhouse — a building in which the Pacers were 35-6 over the regular season — in 22 days.

Truth to tell, the Pacers were fortunate to enter Game 5 not facing elimination. The Hawks wasted a 10-point fourth-quarter lead on Saturday, but lost in the disappointment was a greater truth: Game 4 marked the fifth time in five April meetings, counting the April 6 regular-season game, that the Hawks had held a double-figure lead on the team that’s supposed to be the Eastern Conference’s best.

The Hawks know how to play the Pacers, who still have no idea how to guard the Hawks. Five games into this series, Indiana’s only real defense is to hope the Atlanta 3-pointers don’t drop. For a quarter here Monday, the treys clanked. Then Mike Scott, the second-year pro from Virginia who’s the Hawks’ ninth man, entered the fray and everything — game, series, season — changed.

Scott’s 3-pointer gave the Hawks a 24-21 lead 53 seconds into the second quarter. He would score 17 points in five minutes and 24 seconds. When Scott’s fifth trey of the quarter — that’s correct; his fifth trey of the quarter — sailed true, the Hawks led 48-27. The Naptown crowd was booing hard, but this wasn’t a matter of the Pacers not trying. As crazy as it sounds, the East’s No. 1 seed cannot handle a team that needed a closing kick just to reach the postseason.

Having faced the Hawks six times in April has availed the Pacers not one whit. The Hawks keep running their pick-and-rolls and getting their mismatches and nailing their 3-pointers, and the team that led the league in defensive efficiency stands there and wonders if such a thing is allowed.

In this second quarter, the Hawks scored 41 points. They made nine of their first 10 shots in the period, and the one that missed — a Shelvin Mack 3-pointer — was followed home by the ascendant Scott. The Hawks would lead by 25 points before the half, making this game a reprise of the epic April 6 thrashing here that saw them lead 55-23 at the break.

The Hawks missed three of four 3-pointers in this first quarter. They were nine for 11 — that’s 81.8 percent shooting on shots from 24 feet or more — in the second period. If you’re the Pacers, surely you’re thinking, “They can’t keep making those.” But they can and will if you don’t guard them. Scott was open on all five of his treys. How does that happen?

That Indiana knew what was coming makes this even more remarkable. A No. 1 seed isn’t supposed to keep beating a No. 8 this badly, but this is the No. 8 doing the deed. Before Game 5, Indiana coach Frank Vogel said: “There’s the perception that this horrible eighth seed here that doesn’t belong in the playoffs. Let me reiterate that’s the perception and it’s not shared by me.”

If anything, this No. 8 seed could well cost Vogel his job. He has tried every tweak — from having Paul George try to guard Jeff Teague to deploying two point guards to all but benching the ponderous Roy Hibbert, who finished second in the voting for NBA defensive player of the year — but his team is simply a terrible match for Mike Budenholzer’s.

In his first season as an NBA head coach, Budenholzer has lost Al Horford, his best player, but maximized all remaining parts. For Indiana, the absolute worst matchup is Vogel against Budenholzer.

The series began with the Pacers worried about defending Pero Antic, but now it’s clear that Indiana can’t stop Teague or Paul Millsap or Kyle Korver — or even Mike Scott. The clever Hawks have divided and discombobulated the Pacers, and all that’s left is to put this fraudulent No. 1 to sleep. That will come Thursday.