The quest for financial flexibility that defined the Celtics’ offseason continued on NBA trade deadline day.

After trading third guard Anfernee Simons for veteran center Nikola Vucevic earlier in the week — swapping out one valuable contributor for a player they hope will make a similar impact at a different position — Boston spent the final hours before Thursday’s deadline jettisoning every player who did not hold a rotation role.

The Celtics traded seldom-used big man Chris Boucher, a future second-round draft pick and cash considerations to the Utah Jazz, who promptly waived him. Then, they reportedly sent wing Josh Minott to Brooklyn and big man Xavier Tillman to Charlotte, erasing all of the names at the bottom of their depth chart.

Though the 23-year-old Minott showed versatile 3-and-D potential early in the season and started 10 games, he, Boucher and Tillman have played a total of just 31 minutes since Christmas, the vast majority of those coming in garbage time. Luka Garza, Jordan Walsh, Hugo Gonzalez, Baylor Scheierman and the now-departed Simons have been head coach Joe Mazzulla’s favored reserves for the last month-plus.

Related Articles

Celtics reportedly trade away veteran forward in luxury tax move

Celtics trade rumors: Boston deals young wing to Nets

After trade, Celtics fill open roster spot through internal promotion

Celtics trade rumors: Boston trades big man to Jazz ahead of deadline

NBA trade rumors: Warriors-Hawks deal creates Celtics reunion in Golden State

Still, teams don’t typically ship out all of their non-rotation players in the middle of a season. Why would the Celtics do so? Simple: money.

The Simons-for-Vucevic trade dropped the Celtics below the first apron of the NBA’s luxury tax, removing several roster-building restrictions that limit the types of trades and signings apron teams are allowed to make. The three subsequent deals moved Boston out of the tax entirely — a remarkable change from how its books looked at the end of last season.

Since June, the Celtics have trimmed more than $350 million from their payroll between salaries and luxury tax penalties. Their offseason departures did not tank the team’s hopes of contending, like most expected  — the 33-18 Celtics entered deadline day with the NBA’s best offensive rating, 11th-best defensive rating, second-best net rating and fifth-best record — and this latest round of moves involved only one player who was seeing regular minutes.

(The team had yet to announce the Minott and Tillman trades as of Thursday evening, listing both as out for Friday’s home game against the Miami Heat for personal reasons.)

Boston, which has three games remaining before the NBA All-Star break, now must replenish the back end of its bench — and do so methodically, as it sits less than $1 million below the luxury tax line.

The Celtics filled one of their open roster spots Thursday by converting rookie center Amari Williams’ two-way contract to a standard NBA deal. Williams, a second-round draft pick out of Kentucky, upped his involvement with the big club in recent weeks, serving as Mazzulla’s third-choice big man behind starter Neemias Queta and top backup Garza.

His role likely will shrink following the addition of Vucevic, but Williams already was playing over the far more experienced Boucher and Tillman, so his promotion was no surprise. His contract conversion left the Celtics with three vacancies on their 15-man roster, at least two of which they must fill within the next 14 days to meet the NBA-mandated minimum of 14 players on standard contracts.

Portland Trail Blazers guard Sidy Cissoko (91) and guard Shaedon Sharpe (17) double team Boston Celtics forward Amari Williams (77) during the second half of a NBA game at the Garden. (Photo By Matt Stone/Boston Herald).

Two-way wing Ron Harper Jr. is another candidate for promotion.

The 25-year-old has seen less NBA playing time this season than Williams, but he put together an impressive audition Wednesday night, notching 11 points, nine rebounds and three assists against Houston in his first career start. Harper also blanketed Kevin Durant on defense as the shorthanded Celtics, who were playing without Jaylen Brown, Sam Hauser and Simons/Vucevic, blew out the Rockets 114-93 on the second night of a back-to-back.

Harper is averaging 25.4 points per game for the G League Maine Celtics this season.

Boston’s other two-way players are second-round rookie guards Max Shulga, who made his NBA debut late in Wednesday’s win, and John Tonje, who came over from Utah in the Boucher trade. Tonje has yet to see NBA action.

Now that they are free from apron constraints, the Celtics also can have their pick of veteran players on the buyout market. Clubs above the first apron are barred from signing any waived player whose previous salary was above $14.1 million.

The list of notable names waived on deadline day includes guards Cam Thomas, Mike Conley and Lonzo Ball. The Celtics could be in the market for backcourt help behind Derrick White and Payton Pritchard, who was moved to the bench to fill Simons’ old spot as a second-unit scorer and ball-handler.

The list of current or expected buyout players also includes forward Georges Niang, whom Boston acquired last offseason before flipping him to Utah to sign Boucher, and former Milwaukee Bucks All-Star Khris Middleton.

But after ducking the tax — the first step toward eventually resetting their heavy repeater penalties  — the Celtics surely won’t want to jump right back into it. For that reason, they might need to get creative with the timing and structure of any veteran pickups.