If you watched Markelle Fultz play in the Sixers' opener Tuesday, you probably noticed he got just 3 minutes in the second half. And if you watched the first half, you should have been thinking:

How did he earn 3 minutes in the second half?

You should be thinking now: How long can the Sixers afford to continue the Markelle Fultz Experiment?

Brett Brown warned there would be "growing pains" as he coaches Fultz through his first full NBA season. These weren't growing pains in Boston. These were labor pains.

Fultz is a physiological wonder with unearthly talents, but he's just not much of a basketball player right now. He's bewildered on defense, or lazy, or both. He's skittish on offense, or clueless, or both. Blessed with unbelievable jumping ability, he's Charmin-soft at the rim. He was timid. Toothless. Looking for a place to hide.

Hide him on the bench.

The Sixers won't. For the next few weeks, they will insist that Fultz is only a few dozen NBA games from blossoming. They'll claim they need to start him in place of JJ Redick now so that he can become more than JJ Redick later. They'll talk about Process and Trust and patience. They will be wrong.

Fultz is a young, weak 20. He was playing in his 18th NBA game, and his 43rd game since high school, and he looked like a scared kid. He is nowhere near ready to contribute to a backcourt on a top-tier team. It's unfair to his teammates. It's unfair to the fans. It's unfair to Fultz himself.

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He scored eight points on 2-for-7 shooting. He didn't attempt a three-pointer. Most disturbingly, he finished the game minus-16 — worst on the team — despite playing just 24 minutes, fifth-most on the team. Neither Jayson Tatum, who will forever be Fultz's draft-class comparable, nor Ben Simmons, who will forever be Fultz's franchise comparable, ever had a regular-season game with a minus rating of 16 or more that was worst on the team.

Fultz might have played so badly because he had a touch of Tatum-itis. Bryan Colangelo traded a first-round pick to move up two spots in the 2017 draft to take Fultz over Tatum, who then demolished the Sixers in the playoffs. Fultz watched from the bench, deemed unusable by Brown after missing 68 games during the regular season with a shoulder injury. Tatum torched Sixers again on Tuesday: 23 points, nine rebounds. This time, Fultz was on the court for most of it.

Tatum once agreed that Fultz might be the next James Harden, but that comparison no longer holds. Harden is the most cold-blooded shooter in a league full of gunners and a punishing finisher who invites fouls. On Tuesday, Fultz refused to take wide-open jump shots six times. Worse, he consistently shrank from contact at the rim.

This is grown-folks basketball. You get paid to shoot no matter how ugly your shot is. You get paid to get hit at the rim no matter how much it might hurt, and no matter how weird your free-throw motion might be.

Brown was right. This was painful. Painful to watch.

Sixers guard Markelle Fultz steals the basketball past Celtics guard Kyrie Irving.
YONG KIM/Staff Photographer
Sixers guard Markelle Fultz steals the basketball past Celtics guard Kyrie Irving.

Point guard Kyrie Irving dared him to shoot a three just past 2 minutes into the game, and Tatum dared him later. Celtics center Aaron Baynes dared him twice to shoot from 17 feet; no dice. He was a nonfactor without the ball. Terry Rozier left Fultz open on the wing twice in the first half to make defensive plays 25 feet away.

He went to the rim 2 minutes into the game and missed a bunny. At the beginning of his ruinous third-quarter cameo, Fultz gave up a chance to score or be fouled against Gordon Hayward. Hayward promptly drove hard to the rim at the other end and drew a foul. After a few decent moments in the first half, Fultz spoiled whatever good feeling he'd produced. He was disinterested, disengaged and more than a little confused. He did not play in the fourth quarter.

That Fultz struggled against the Celtics should surprise no one. It didn't surprise Brown, who said Monday that the season should not be defined by what would happen Tuesday. He knew that Boston coach Brad Stevens, who engineered a stifling defensive scheme in the second round of the playoffs that won the series in five games, would have no problem using Fultz to his advantage.

The Celtics are the class of the conference, so Fultz might be more effective in Thursday's home opener against the Bulls, or when the Magic visit Saturday night. Or, he might not be. Brown has mentioned that it might take as many as 20 games for the Sixers to form an identity. It took them 50 games last year.

But can the Sixers afford this sort of burden for 25 percent of the season? Apparently, they're going to try, at the expense of Redick, who has lost his starting spot, and T.J. McConnell, who would gnaw off your ankle if it meant winning a loose ball.

Maybe it's all for the best. Brown has been right before. He switched Simmons from power forward to point guard. He let center Joel Embiid develop a 25-foot game. He created Robert Covington and McConnell from scratch.

Maybe Redick, now 34, should play 25 minutes instead of 30. Certainly, Fultz's size and athleticism, once developed, will eclipse McConnell's limited value.

Then again, in light of the Sixers' stated intentions to land one of the offseason's big three prizes – LeBron James, Paul George, Kawhi Leonard — maybe Brown & Co. are just trying to sell Fultz as the upgrade the Sixers needed but failed to get.

We all understand salesmanship. But this product isn’t ready for the market.