The Boston Celtics are crawling toward the finish line of the regular season. After looking invincible for much of the first half of the season, the C's have gone just 7-6 since the All-Star break, losing control of the top seed in the Eastern Conference and barely holding onto the second seed ahead of the Philadelphia 76ers. And as the playoffs draw near, all eyes are going to turn to Boston's first-year head coach Joe Mazzulla.

Mazzulla took over for the C's right before the start of the season after Ime Udoka was strangely suspended for the entire season by the Celtics. Mazzulla had no NBA head coaching experience and had the tall task of guiding a talented Boston squad on a deep playoff run despite that lack of experience. But the C's were so good early on that Mazzulla had his “interim head coach” job title get cut down to just “head coach” during the All-Star break.

As we know now, though, the Celtics have been a complete mess since the break. Their offense cannot find ways to score consistently, and their defense looks lazy and uninterested in slowing down their opponent. It raises the question of whether Mazzulla is actually a good coach or a coach who coasted off the success of his players. Whichever way you slice it, it's beginning to look like Boston made a big mistake with Mazzulla.

The Celtics have made a mistake with Joe Mazzulla

Heading into the All-Star break, there was really no reason to be overly concerned with Mazzulla becoming the Celtics' official head coach rather than just the guy holding down the fort in the interim. Boston had been the best team in the league all season long, and while Mazzulla's coaching strategies were a bit unorthodox at times, they seemed to be working quite well for the team.

After this 7-6 run, though, all of that has gotten thrown out the window. The C's have looked lost, and Mazzulla hasn't been able to do anything to right the ship. He's been able to get by through the regular season without having to prove much, but with the playoffs nearing, Mazzulla is going to be thrown into the spotlight. And quite frankly, that is an extremely worrying proposition.

Regardless of the team's recent cold stretch, what has Mazzulla shown this season to indicate that he is going to be able to outcoach guys like Mike Budenholzer or Doc Rivers in a seven-game playoff series? Last season, Ime Udoka turned Boston into a defensive juggernaut to help overcome their inconsistent offense. Mazzulla has shown nothing of that sort this season.

Maybe he's a master strategist just waiting to show the world, but there have been issues with Joe Mazzulla's coaching all season long that have been glossed over because the Celtics were winning. But now that they aren't winning, those issues immediately become more concerning, and serious doubts about Mazzulla's coaching abilities are beginning to arise.

Let's start with the team's rotation. It is obviously going to be tough to figure out given the assortment of talent on this team but Mazzulla hasn't been able to carve out a consistent rotation all season long. Marcus Smart is still getting crunch time minutes over Derrick White and Malcolm Brogdon despite playing marginally worse than both guys this season, and he's ostracized Grant Williams and Payton Pritchard with wildly inconsistent minutes.

In terms of his in-game coaching, Mazzulla doesn't have a great track record either. His penchant for not calling timeouts is becoming increasingly frustrating, and he hasn't proven adaptable to when teams make adjustments and begin to thwart the C's on both sides of the ball. We have seen massive leads get blown by Boston, and close late games thrown away, partly because of Mazzulla's incompetence on the sidelines.

The Celtics rode their talent to a flaming hot start to the season, but teams have picked up on what they do, and Mazzulla has had no answers for those adjustments. On offense, Mazzulla would seemingly be OK if Boston took a three on every possession, as they have no consistent interior scoring currently. Defensively, the Celtics, who were the best defensive team in basketball last season, have looked like a shell of themselves.

The concern regarding Mazzulla has been mounting for some time, and unless he can pull a rabbit out of his hat and find a way to miraculously fix Boston's issues, this team is going to be in trouble. Mazzulla has been thrown into quite a difficult situation, but the Celtics have title aspirations that are fading in front of their eyes partly because of his poor coaching.

That's why the team made a mistake lifting the interim tag off of Mazzulla's job title. You don't prove anything by having the best record in the NBA at the All-Star break; you prove it by winning in the playoffs. Joe Mazzulla has faced an incredibly difficult task for his first NBA head coaching gig, but he's letting his team down right now, and for the Celtics, that should be an increasingly worrying proposition as the playoffs draw near.