The Boston Celtics are back to their frustrating ways it seems. After playing two of their best games of the season in Games 6 & 7 to dispatch the Philadelphia 76ers and move onto the Eastern Conference Finals, the Celtics threw away a 13-point lead against the Miami Heat, and ended up losing the series opener between the two squads 123-116.

It's quite irritating that performances like this are becoming common from the Celtics, but here we are. The C's were in complete control of this game as the first half came to a close, but watched the gritty Heat battle their way back to take as big as a 12-point lead thanks to a 46-point third quarter. Boston battled in the fourth, but ultimately couldn't overcome such a sizable gap.

This is who the Celtics are, and who the Heat are as well. Just when you think Boston has finally figured out their recent ECF foe in Miami, they storm back and pull off the same comeback we have seen them complete a handful of times on the same stage. It's only one game, but there were three particularly concerning trends that popped up throughout this game that need to be addressed immediately ahead of Game 2

3. Celtics aren't taking enough three pointers

This game felt eerily reminiscent of the Celtics Game 1 action against the Sixers in the semifinals. Boston was getting pretty much whatever they wanted in the paint in the first half, and once Philly adjusted in the second half, the offense quickly disappeared. This is largely due to the Celtics failing to shoot enough threes and missing a handful of the open looks they generated.

Boston finished the game shooting just 10/29 from behind the arc, which is pretty similar to the 10/26 shooting performance they had from three in Game 1 against the 76ers. The Celtics became enamored with attacking the paint, but once the Heat adapted, they were unable to switch gears.

The C's were able to overcome this strange shot diet against the 76ers last series, and chances are they will be able to do the same thing in Game 2 and beyond. But Boston has to recognize that they often are a team that lives or dies by the three, and when the game gets down to the nitty-gritty, it's nice to have their best players in rhythm from behind the arc. In Game 1, that simply was not the case.

2. Celtics did not get Jayson Tatum the ball nearly enough in the second half

While Marcus Smart and his ten assists drew quite a bit of praise in the first half, it was clear that Jayson Tatum was Boston's best player during the opening 24 minutes. Tatum dropped 18 points in the first half, and was getting whatever looks he wanted. Tatum was switching onto overmatched Heat defenders in their 2-3 zone, and with Bam Adebayo getting pulled out of the paint, he was hitting some of the easiest looks of his life.

For whatever reason, the Celtics decided to completely go away from Tatum in the second half. He didn't take a single field goal in the fourth quarter, with his only points coming from the free throw line, and when Joe Mazzulla decided to try to get his best player involved late in the game, he was goaded into a series of turnovers that effectively iced the contest for the Heat.

It's really inexplicable that Boston went away from Tatum, given how good he was playing in the first half, and how the C's scored just 50 points in the second half. Tatum cannot be allowed to sink out of the offense like this moving forward; we have seen similar things happen to Jaylen Brown, who was surprisingly given the keys to the offense in the second half, despite a fairly inconsistent outing. Tatum still dropped 30 points, but he needs to be way more involved moving forward for Boston.

1. Celtics basically refused to play any defense against the Heat

The offensive struggles should figure themselves out, but easily the biggest concern from this game was Boston's defense. Miami went from averaging 104.3 points per game against the New York Knicks to hitting 54.1 percent of their shots from the field, including 51.6 percent of their threes in Game 1 against the C's. There's obviously going to be a bit of regression to the mean moving forward, but the Celtics made everything way too easy for them on offense.

There was so much wrong with the defensive gameplan in this one. Mazzulla decided that everyone on the Celtics could defend Jimmy Butler, which he quickly proved wasn't the case. Boston's two best wing defenders in Tatum and Brown did the best job defending Butler, but pretty much every other switch he got, he capitalized on. Similar to how Brown stuck to James Harden like glue against the Sixers, he or Tatum needs to do the same thing against Butler.

Miami's reserve players won them this game, but again, the Celtics were barely covering them. The amount of uncontested midrange or three-point jumpers in this game was astounding. Guys like Gabe Vincent (31.8 shooting percentage against the Knicks) and Kevin Love (31.6 shooting percentage against the Knicks) went from being ice cold to knockdown shooters because the Celtics let them.

This was a horrible way to open the series defensively, and changes need to be made. Brown and Tatum should be the only defenders of Butler, as they cannot afford to constantly switch on him. And for the reserve players, more pressure needs to be applied on the perimeter to limit their sudden hot-shooting from behind the arc. Miami isn't going to shoot above 50 percent every game, but the Celtics can open up their offense by playing strong defense, and they will need to make these changes before their suddenly crucial Game 2 contest.