The Hawks left St. Louis in 1968. This marks the 34th time over 53 Atlanta-based seasons they’ve made the playoffs. Only four times have they won a Round 1 series that, going by standings/seedings, they weren’t supposed to win. The victims of those upsets: Houston in 1979, Indiana in 1996, Orlando in 2011 and …

The New York Knicks in 2021.

Already this postseason is different. In half of those postseason appearances, they were gone after Round 1. The only time they’ve won two series came in 2015, when they won 60 games and were the East’s No. 1 seed. They were swept in the conference final by Cleveland/LeBron. They made the Western Division final (when there were no conferences, only two divisions) their first two seasons here; once there, they went an aggregate 1-8 against the Lakers of Wilt and West.

When the Hawks do make the playoffs, they seldom exceed expectations. If you’re listing Atlanta’s most stirring NBA memories, two came in lost Game 7s – in Landover, Md., against reigning champ Washington in 1979 and the Bird-Dominique duel in Boston in 1988. Seldom has this team been a pleasant surprise. These Hawks already are an exception.

Their Round 1 dismissal of the Knicks technically was an upset, though from Game 1 on it was clear they were the better side. They’re a decided underdog in Round 2 against top-seeded Philadelphia, but this series looks mightily inviting, too. Joel Embiid, the 76ers’ best player, has a torn meniscus. As we’ve seen from recent examples – from Kevin Durant to Anthony Davis – guys who try to play hurt in the postseason tend to get worse, not better.

If Embiid indeed isn’t himself, the Hawks can win this series. Granted, it wasn’t so long ago we wondered if these Hawks would win another game. That changed when Nate McMillan became interim head coach. His Hawks are 31-12, counting playoffs. That’s a winning percentage of .721. The Sixers’ winning percentage this season, also counting playoffs, is .688. The Hawks’ dismissal of the Knicks wasn’t the usual tight 4-versus-5. The Hawks won breezing. There’s a real chance this Eastern semi will be way more competitive than an ordinary 1-versus-5.

Nobody knows what the Hawks’ ceiling is. They were terrible under Lloyd Pierce. They’ve been excellent under McMillan. We saw some of this coming in April. The Hawks beat Miami, which reached the NBA Finals in the Disney bubble, without Trae Young and Clint Capela. Two nights later they beat Milwaukee with Capela but still without Young. It’s silly to assign vast importance to regular-season games – different teams have different agendas – but those results made us take note.

Seven Hawks averaged 9.4 points or more over the five games of Round 1. Only four Knicks did. That was your series right there. The Hawks haven’t just built a starting five; they’ve constructed a rotation. They’ve put shooters around Trae Young. They have Clint Capela underneath. Kevin Huerter has been terrific as a reserve. De’Andre Hunter was much of the reason why Julius Randle made but 29.8 percent of his shots.

As of March 1, we weren’t sure the Hawks had much of anything. Since promoting McMillan, they appear to have pretty much everything. They out-defended the Knicks, who led the NBA in defense. They have the league’s leading rebounder. Oh, and they have Young, who averaged 29.2 points and 9.8 assists in the series and hit the winner in Game 1, from which the New Yorkers never recovered.

The Hawks are among the league’s more talented teams. That so much of the team is young talent makes it even better. These guys aren’t apt to revert to sub-mediocrity. They’ve seen how good they can be. They’ve begun to believe.

Some on the outside might still be wondering. The Knicks were an overachieving team that couldn’t rise to its playoff moment. The Sixers will be tougher, unless Embiid can’t go, in which case the Hawks would spring from underdog to favorite. If that sounds nuts, survey the landscape. LeBron’s team is out. Steph’s team is out. Kawhi’s team is teetering. Dating to 2011, every champion has been led by one of those three.

Of the four teams left in the East, none has won an NBA crown since Philly in 1983; none has reached the finals since the Nets in 2003. There’s no form for what’s about to happen. In the absence of usual suspects, new contenders are bound to emerge. Why not the Hawks?

Said McMillan, speaking Friday: “We still believe. We’ve always talked about that – believing that we can win the game out in front of us. That doesn’t change for us. We did win a series, and we’re into the second round. The belief is that you can win (Game 1) on Sunday.”

Over the three seasons preceding this, the Hawks were 73-158. They were 14-20 on March 1. Forget doing damage in the playoffs: On the day Pierce was fired, this team wasn’t positioned to qualify for the play-in tournament. But here it is, flying into Round 2 on the wings of one of the most impressive playoff performances in franchise history – emboldened by what just happened, enthused about what still might.

The Lakers are out. The Celtics are out. The Hawks are still going. They mightn’t stop anytime soon.