The Sixers already bet big on Tobias Harris. Their best course of action is to see if it pays off. | David Murphy

The Sixers knew this day was coming. They knew it when they traded Robert Covington and Dario Saric for Jimmy Butler, and they knew it when they traded Landry Shamet and two first-round picks for Tobias Harris, among other players and picks.

They knew who Butler and Harris were. They knew what it was going to cost them to keep them in the fold long-term. And whatever doubts they might have had about the fit between their skill sets and those of Joel Embiid and Ben Simmons, they now know that they were three points — or, perhaps, a couple of fateful bounces — away from eliminating a team that needs just three more wins to claim an NBA title.

That, right there, is the strongest argument for paying what needs to be paid to keep the gang together. It’s also the best place to start when you sharpen your No. 2 pencil or fire up your Excel spreadsheet and attempt to figure out how much sense it makes to keep Harris in the fold.

From there, a series of observations follows . . .

1) The Sixers’ payroll will be substantial, but it will not be crippling. At least, not at first.

Like Butler, Harris is eligible to sign a five-year contract worth roughly $188 million. That’s one more guaranteed year and $40 million-plus more in guaranteed dollars than any other team can offer him, thanks to the Sixers’ possession of his Bird Rights. As our Keith Pompey has reported, the Sixers have little choice but to assume that it is going to take the entirety of that sum to keep Harris out of the clutches of another team.

If the Sixers were to sign both Harris and Butler to max deals while also bringing back JJ Redick at the same salary as last year, it would leave them roughly $8 million under the luxury-tax threshold with four-to-seven roster spots left to fill. Even if they surpassed that mark by adding a couple of veterans on minimum deals and one using their $4 million room exception, their tax bill would be minimal.

2) Starting in 2020-21, things could get dicey.

Assuming that their summer culminates in the signing of Ben Simmons to a max extension, they would have four players making $29 million-plus under contract in 2020-21. To put that in perspective, no other team in the NBA had more than two such players in 2018-19. The Sixers would almost certainly become one of the most top-heavy teams in the league in terms of payroll allocation. With Jonah Bolden, Zhaire Smith, and the No. 24 pick in this June’s draft all also under contract, the Sixers would be sitting right at the luxury-tax threshold even if they carried only 12 players, with five making the rookie minimum. They’d have about $7 million in room before the luxury-tax apron, a mark at which their roster maneuverability would be reduced even further. Essentially, the Sixers would be relying on Smith, Bolden, and this year’s first-round pick, plus any veteran-minimum players, to round out the rotation behind the Big Four.

3) There might not be any better options out there.

In order to avoid wasting too much space summarizing the NBA’s accounting procedures, it’s probably best to focus on one key takeaway. Even if the Sixers were to part ways with Harris, they wouldn’t suddenly have five years and $188 million to dole out to some other free agent or collection of free agents. Rather, that number would be more like four years and $86 million. Remember, they can go over the cap to sign Butler and Harris, the latter of whom is currently on the books as a cap hold in the neighborhood of $22 million, which is $10 million less than he’d earn in Year 1 of a new max deal. Removing Harris from the books would leave the Sixers around $20 million under the cap. Depending on how the market plays out, that could be enough to sign someone like Malcolm Brogdon or Nikola Mirotic to take Harris’ place. But that’s hardly guaranteed. It could also be enough to sign someone like Patrick Beverley to a four-year deal in the $50 million range plus another lower-tier free agent. But, again, that’s hardly guaranteed.

4) The upside of a player like Harris can only be guaranteed with one player -- Harris.

In the 27 regular-season games that Harris played for the Sixers, he shot just .326 from three-point range, a dramatic departure both from the .434 he shot for the Clippers in 55 games before the trade and the .411 he shot during the 2017-18 regular season. He’s 26 years old. With more time to grow into a role alongside Butler, Embiid, and Simmons, there’s no reason to think he won’t again become the shooter he has developed into over the last handful of seasons.

It will be expensive. But, in all likelihood, it’s the Sixers’ best option.