The Celtics' biggest offseason adjustment should start with Marcus Smart

Before we begin, let’s make one thing clear: The Celtics lost Game 6 against the Heat first and foremost because of their defense. It was the worst defensive outing of the postseason (125 points allowed per 100 possessions) for Boston and third-worst defensive night all season long for the C’s. Incredibly, Boston had won their worst two defensive showings in the regular season by winning shootouts against two of the worst defenses in the NBA this season (Portland, Washington). They weren’t so lucky against the Heat on Sunday night.

Miami deserves credit for its standout Game 6 performance offensively. Bam Adebayo played the game of his life (career-high 32 points), which opened up the floor more for his teammates down the stretch. The Celtics made defensive mistakes all night but the Heat also hit tough shots when the C’s were contesting. Outscoring the Heat, as opposed to slowing them down, was going to be the only way to win Game 6, something that has been evident with their clutch play all postseason.

The Celtics managed to do that for the better part of three quarters, building a six-point lead with just under nine minutes remaining in the fourth quarter. However, it all came crashing down late as the team leaned heavily into its 3-point shooting late (2-of-14) after the Heat baited them into doing so against a 2-3 zone. A breakdown of the C’s shot attempts tell the story.

Fourth quarter stats

Celtics

2pt FGs: 8/13
3pt FGs: 2/14
FTs: 5/7

Heat

2pt FGs: 9/15
3pt FGs: 3/3
FTs: 10/13

Everyone had their fair share of struggles down the stretch from Kemba Walker (1-of-6 from 3-point range) to Jayson Tatum (2/6 FG). You live with your All-Stars having bad shooting nights when it matters. However, a look at the box score for the game and second half reveals another disturbing trend that came back to bite Boston in this series.

Game 6 shot attempts

Tatum: 27
Smart: 22
Brown: 17
Walker: 15

Those 22 shot attempts for Smart were a postseason career-high (his previous was 18). It was also the third most attempts he’d taken in his five-year career. The numbers get worse when you break it down into just the second half.

Game 6 second-half shot attempts

Smart: 13
Tatum: 11
Brown: 11
Walker: 10

With the Celtics season on the line, a sub 40 percent shooter led the C’s in shot attempts. Regression hit hard for the Celtics and Smart in Game 6 (he missed his final seven 3-point attempts on the night after opening 4-of-6) but a high-volume shooting Smart is something that this team should no longer have to worry about at this stage of his career given the evidence.

Put simply, the Celtics are not a good team when Smart tries to become a lead dog. Boston was 8-12 in the regular season when Smart attempted 13 or more shots. They were 2-6 in the postseason when he did the same.

There are times when the Celtics need to ask Smart to do more offensively. He’s made incredible strides with his 3-point shooting in the past two seasons and helped carry them to a win in the Raptors series when Toronto elected to shut down Kemba Walker and dared Smart and Jaylen Brown to beat them.

The equation was different against the Heat all series though, especially once Hayward came back. A 2-3 zone defense that Miami played opened up good looks for everyone, not just Smart. Yet, Smart treated himself like a top-tier scoring option, taking a larger share of shots than was necessary when there were far superior options available. Jaylen Brown shot 55 percent from the field against Miami and 50 percent from 3-point range yet he finished with five fewer shots than Smart in Game 6. That's inexcusable.

“I was just trying to step in and provide what my team needed with a guy down,” Smart said. “And that's in all aspects, from scoring the ball, to playmaking, to just being there on the defensive end and things like that. That's part of the game. It was my opportunity to step up and bring that. You know, it might be somebody else's. You just got to be ready when your number is called. You have to give everything you can to help your team win.”

Smart’s shots going elsewhere in Game 6 wouldn’t have guaranteed a Celtics win but Smart taking so many help increase the odds of a loss. His fourth quarter struggles during the series were eye-opening as well.

5/18 FG, 1/8 3pt, 8 assists, 7 turnovers

At this stage of his career with the kind of offensive talent Smart has around him, he needs to embrace his role more of a distributor and defensive menace in big moments. He was neither in the fourth quarter of Game 6. Whether it was a bad 3 or an ill-advised turnover, he cost the Celtics time and time again in this series when it mattered most.

In a perfect world, Brad Stevens would have been able to go with Gordon Hayward at 100 percent over him along with a big (Daniel Theis/Grant Williams) in crunch time on offensive possessions if he wasn’t willing to defer more but Hayward’s injury prevented that option. Stevens’ inability to reel Smart in on this front during Game 6 was costly. An added reliable bench piece certainly would have helped but Danny Ainge did not find the right match at the trade deadline, putting added onus on Smart and the rest of this core throughout this playoff run that came back to bite.

As the calendar turns to the 2020-21 season and limited meaningful options are available to improve this team due to salary and luxury tax restrictions, internal improvement is the best bet for the Celtics to get over the hump. The Celtics need Smart for his top-level defense, passing and ability to knock down an open 3. However, they also need him to be willing to create for others more than himself when a game is on the line, something that has been an issue all season long. The sooner he understands what his role needs to be in those spots, the better off the Celtics will be.