Are the Celtics really all-in on head coach Joe Mazzulla?

ESPN's Brian Windhorst recently said the Boston Celtics never considered firing head coach Joe Mazzulla. That's surprising given the team’s inconsistent play in the postseason and at least one player being upset with the rookie sideline boss.

Windhorst, who made the comments on a recent episode of his own podcast, "Brian Windhorst & The Hoop Collective," believes the club’s offseason moves are a way of showing support for Mazzulla.

Consider that Marcus Smart, an elite defender, was shipped to the Memphis Grizzlies. Also, forward Grant Williams was practically encouraged to sign a below-market deal for the mid-level exception with the Dallas Mavericks as part of a three-team sign-and-trade that only landed the Celtics two second-round draft picks.

While trading Smart brought back an impressive haul in talented post Kristaps Porzingis and two first-round draft picks, the deal was made, in part, because his outspoken leadership style sometimes clashed with the understated Mazzulla.

Williams, a versatile defender with three-point range, failed to get consistent playing time for most of the regular season. In the Eastern Conference Finals, it was hard to tell if Williams was more frustrated with guarding Miami Heat star Jimmy Butler or Mazzulla’s sporadic substitution patterns.  

Both players are gone, and the team should be to easier manage. After all, Brad Stevens — the former Celtics coach turned lead executive and ally of Mazzulla — replaced Smart and Williams with Porzingis and Oshae Brissett, a July free-agent signing, to allow the coach to implement the free-wheeling, offensive style he prefers.

There are concerns with these changes, though. 

Porzingis averaged 23.2 points and 8.4 rebounds in 65 games for the Washington Wizards last season, but he missed 95 games in the previous four seasons. Porzingis could cause a logjam with established posts Al Horford and Robert Williams, who have their own health issues. 

An athletic wing with size (6-foot-7, 210 pounds), Brissett saw his production fall off the past two seasons with the Indiana Pacers.

The dynamic between the head coach and his new assistant coaches will be worth watching, too.

Mazzulla, who took over for Ime Udoka under difficult circumstances on an interim basis last summer, had a 57-25 record and was given an extension before the playoffs. Fair or not, there was always a feeling Mazzulla was riding the momentum of the previous season, and his entire staff’s lack of experience would get exposed during the playoffs. That's what happened.

Enter Sam Cassell and Charles Lee, Boston's recent hires as assistant coaches. While both will support Mazzulla, Cassell and Lee have NBA experience at a high level and could make good head coaches. Cassell spent three years as an assistant on Doc Rivers' staff in Philadelphia. Lee was Milwaukee's associate coach last season.

If the inconsistent play from May continues and the Celtics get off to a slow start, Cassell and Lee could be options to replace Mazzulla. These Celtics will soon become especially expensive, with massive extensions coming to stars Jaylen Brown and Jayson Tatum.

Support, specifically the kind Mazzulla has received this summer, might be a luxury Stevens and ownership can’t keep giving.