“I’m old and I’ve never experienced anything like this,” Sixers coach Brett Brown said Monday. “This” is an ordeal that started in September, when Markelle Fultz showed up to training camp with a jumper that looked like Charles Barkley’s golf swing. Fultz hasn’t played since October 23, when the team shut him down because of shoulder soreness and “scapular muscle imbalance.” The no. 1 overall pick in last year’s draft is back to practicing, but his shot still looks broken. Brown said Fultz won’t play until he can “shoot a basketball.”

Joel Embiid tweeted after Fultz’s June 17 predraft workout that it’d be “legendary” if Fultz joined forces with the Sixers; no one would have expected it to be such a legendary bummer. Fultz shot 41.3 percent from 3 in college. Every site had him ranked first; most NBA execs did too. The Sixers traded the rights to the third overall pick (Jayson Tatum) and a protected first (either the Lakers’ or the Kings’) to the Celtics for no. 1 overall in order to select Fultz. It looked like a wonderful fit, with Fultz complementing Embiid and Ben Simmons. But now Fultz is uncomfortable with something as basic as shooting.

Fultz’s basketball stupor is the weirdest story in sports. Not even the most cynical Process doubter could’ve seen this coming, and where he goes from here is just as much of an unknown.

But even if Fultz turns into a bigger bust than Anthony Bennett, the trade that brought Fultz to Philly could have a legacy of its own. Entering the 2017 draft, there were 10 prospects that had a chance to become the class’s best player. Sixers GM Bryan Colangelo said there were five or six surefire All-Stars. One front-office executive compared the list to the top 10 from 1999, which featured five multitime All-Stars and four starters.

A high-level front-office source told me, and Ainge later confirmed, that both the Sixers and Celtics felt there was little separation between the no. 1 and no. 3 picks. The deal simply allowed both teams to select their preferred player. By making the deal, the Sixers guaranteed they’d get Fultz, even if it meant giving up an extra asset to do so. The Celtics, meanwhile, got a player they probably still would’ve taken at no. 1 and another asset for their trouble. That formula may work in this year’s draft, too.

Historical numbers from 1980 through 2012 show that the no. 1 pick has been a multitime All-Star 69.7 percent of the time, per the Draft Express pick-expectations tool. The odds drop to 45.5 percent at no. 3 and 27.3 percent at no. 5. But not every class is created equal. The 2017 class was uniquely loaded, and so is 2018’s. There were five potential “best prospects in the class” entering the season: Luka Doncic (Real Madrid), Deandre Ayton (Arizona), Marvin Bagley III (Duke), Michael Porter Jr. (Missouri), and Mo Bamba (Texas). And now Trae Young (Oklahoma) has become the sixth. That list is unlikely to change, though Jaren Jackson Jr. (Michigan State) or Collin Sexton (Alabama) could play themselves into the conversation. Even six high-level prospects would create an atmosphere ripe for a trade-down similar to the Fultz-Tatum exchange.

I banged the trade-down drum last May and again in June — not because I thought it would happen, but because it made sense, given the depth at the top of the draft. As draft coverage ramps up the next few months, keep in mind that teams will rate these players differently. Even if Doncic is the top-ranked player on every website, it doesn’t mean that he’s the prize for your team. Some teams will prefer Ayton over Bamba. Others will want Porter. If Kings owner Vivek Ranadivé saw Stephen Curry in Buddy Hield, then he must have found the meaning of life in Young. Consensus is a myth.

Any trade depends on each general manager’s rankings and objectives. Teams that are more than one player away from contending could find value in trading down to pick up an additional asset. If the Mavericks, a team now rebuilding for its post-Dirk era, were to win the lottery, what would be preferable: picking Bagley or trading down for Bamba and a protected 2019 first from the Suns? Or if you’re a Hawks fan, do you want Doncic or Porter plus other assets? It all depends on your personal preference.

There’s also value in keeping the draft cupboard stocked, much like the Celtics did last season. Adding the Lakers’ or Kings’ protected first-rounder allowed Boston to be more comfortable with sending out the Nets’ 2018 first-round pick in a deal for Kyrie Irving. There’s nothing stopping the Celtics from doing it again if the Lakers pick conveys. Any team hoping to position itself to pounce on the next available superstar could do the same.

But deals like this are a rarity. There have been only 13 trades since 1980 in which a team with a top-five pick moved down in the draft. And it doesn’t always work out for the team giving up the higher pick. For instance, the Grizzlies got burned in 2008 by trading the rights to no. 5 pick Kevin Love for the rights to no. 3 pick O.J. Mayo. The Bulls did the same in 2006 by swapping the second pick, LaMarcus Aldridge, for a package featuring no. 4 pick Tyrus Thomas.

And the path isn’t always an easy one. Ainge was grilled by local sports-radio pundits and questioned by many Celtics fans for trading down out of fear of missing out on a hyped-up top prospect. But teams can’t have FOMO. They have to trust their scouting evaluations. Members of the Timberwolves’ front office had strong interest in Paul George in 2010, but the team ended up going the conventional route and taking Wesley Johnson with the no. 4 pick. That was a mistake.

All eyes will be on Tatum on Thursday, as the Celtics face off against the Sixers on national TV. Fultz, meanwhile, will be in a suit. There will be discussions on the broadcast regarding Philadelphia’s decision to make the trade and Fultz’s future. It’s too soon to say that the Sixers made a critical error. But what the Celtics did could set a precedent for a similar deal in June.