Say this for these Celtics: They fight. After Gordon Hayward's gruesome injury -- later determined to be a broken lower leg and displaced ankle -- understandably rendered them lifeless and the Cavaliers ran out to an 18-point lead, Boston battled back in its disheartening season-opener. 

While the Cavaliers won 102-99 Tuesday in a wild affair, the first game of this NBA season seemed to suck the life out of fans everywhere in the first quarter. One look at the bench reaction from Hayward's injury tells the story:

Right away, the support for Hayward started pouring in on Twitter. LeBron James went to see Hayward as he was being checked out in the Cavaliers' home locker room. So did Isaiah Thomas, who of course recruited Hayward to join him in Boston before he was traded to Cleveland. It's too early to speculate how long Hayward will be out, but worries already have surfaced that his season could be over. 

You have to wonder if the same is true for the Celtics, who were coming into the season with so much momentum after Danny Ainge finally put together the kind of blockbuster summer people had long been waiting on. With Hayward, Kyrie Irving and Jayson Tatum on board, Boston was supposed to be at least an outside threat to the Cavs in the East. Hayward's absence would put a major damper on that.

And that's a shame. It's a shame for Hayward, for the Celtics, and it's really a shame for the fans, many of which were starving for some true competition in the East after Cleveland went 12-1 through the conference playoffs last season. Here are SportsLine data expert Stephen Oh's new Celtics projections without Hayward: 

BOSTON CELTICS

WIN

LOSS

WIN%

PLAYOFF

SEED

EAST

CHAMP

w/ Hayward

53.0

29.0

64.7%

99.9%

#2

28.12%

4.65%

w/ Hayward Out Season

48.3

33.7

58.9%

95.8%

#3

11.34%

1.10%

IMPACT

-4.7

4.7

-5.8%

-4.1%

-1

-16.78%

-3.55%

Clearly, the Celtics are going to have to show the same kind of resilience moving forward as they did in going on a 28-11 run to enter the fourth quarter trailing by just one. Indeed, there were a lot of positives to take from the Celtics' opener. Marcus Smart, who didn't get his contract extension, was everywhere in the third quarter. He still didn't shoot a lick (0 for 9 in the first half), but he's quickly beginning to feel like a mini Draymond Green with the effect his energy and position-less defense has on his team. 

Jayson Tatum was solid in scoring 14 easy points, including some big buckets down the stretch, while becoming the first Celtics rookie since Larry Bird to notch a double-double (10 boards) in his NBA debut. Jaylen Brown looked more aggressive than he has at any point in his early career, going hard to the rim, stepping confidently into 3-pointers, posting 25 points and six boards. Al Horford was quietly effective in all areas. And oh yeah, about that Kyrie Irving guy. 

Making his Celtics debut under some very difficult circumstances -- he was booed in his return to Cleveland, and he looked genuinely shook after Hayward's injury -- Irving played like a man ready to be the man. It wasn't just the 22 points, the 10 assists, or the three steals -- it was the measured way he ran his game, and Boston's offense, picking his spots to score while getting everyone involved. It all looked very easy -- his tempo, his control, everything. Every Celtics player looked smoother alongside him. 

Which only makes it all the more disappointing to watch Hayward go down like he did. Watching the Celtics fight the way they did in his absence, seeing Irving have that kind of effect on the play of his new teammates, it's evident what this team had a chance to be this year. This really is a tough one to swallow.