After losing on opening night to the 76ers, the Boston Celtics ran off 10 straight wins to open the 2019-20 season in becoming one of the league's best early stories. The headlines wrote themselves. Kyrie Irving, the scapegoat, was out. Kemba Walker, the savior, was in. Jayson Tatum, Jaylen Brown, Marcus Smart and Walker had spent summer playing together for Team USA, and their resulting chemistry was apparent. Nobody was fighting for the ball. Everyone was defending. 

All was great in the land of the Green. 

And for the most part, it still is -- entering play on Tuesday night, the Celtics are the Eastern Conference's No. 2 seed with a 27-11 record and the third-best net rating in the league. But before we get too far ahead of ourselves, let's remember that Kyrie got off to the same fairytale start that Kemba has in Boston. 

Indeed, the 2017-18 Celtics won 16 straight games after dropping their opening two. Through 36 games that season, in fact, the Celtics were 29-7, four games better than this year's squad, and Kyrie was on the fast track to becoming the next Boston sports hero. 

In other words, great starts don't necessarily equal great finishes, and there has been some leveling out for this year's squad as the inevitable turbulence of an NBA season has popped up. All told, the Celtics are No. 4 in defense and No. 5 in offense. Again, things are still really good. But they're not over-the-moon great anymore. 

Since starting 10-1, the Celtics are 17-10 with just four wins over plus-.500 teams. Per ESPN, in fact, Boston has had the second-easiest schedule in the league to date. That doesn't invalidate anything it has done, but it's information worth considering, and it surely forecasts a challenging road ahead. 

Are the Celtics up for it? Will Danny Ainge look to bolster the roster with a deadline deal? We'll have to wait and see. For now, with the information we have, let's break down how the Celtics have gotten to this point with a midseason report card. 

Kemba-for-Kyrie flip: A

The Celtics have had to answer questions about Kyrie Irving all season. Marcus Smart finally got sick of it, understandably. But there's no denying that Kemba has taken this Boston team's collective frown and turned it upside down. One scout told me he believes Kemba "probably isn't individually quite as great as Kyrie" but is "much better for the Celtics' other players." 

The scout had an interesting theory: That players aren't as afraid to screw up when they're playing alongside Kemba, who feels like one of the guys, as opposed to Kyrie, who perhaps "projects more of a superstar intimidation." 

The player that has probably benefited most from Kemba's more lighthearted presence is Jaylen Brown, who is in the All-Star conversation with a more empowered role this season. At this time last year, Kyrie had assisted on 22 of Brown's makes, while Kemba has already connected for 39 assists with Brown. There's context to that. Brown is making more shots this season. 

But perhaps that's partly the point?

Kemba and Kyrie play similarly -- heavy pick-and-roll, a lot of individual, dribbling-display creation. Walker, in fact, is holding the ball for longer per touch this season (5.13 seconds, per NBA.com) than Kyrie did with Boston last season (4.27 seconds), while also dribbling more times per touch (4.71) than Kyrie did last season (3.91). 

So the theory about Kyrie being too ball dominant for the other Celtics to feel involved doesn't necessarily hold water, at least not statistically. In fact, last year's Celtics, on average, made 16 more passes per game than this year's team does. 

Per Synergy, Kyrie of last season and Kemba of this season are nearly inseparable as offensive producers (points + assists). 

  • 2018-19 Kyrie: 1.36 points per possession 
  • 2019-20 Kemba: 1.31 points per possession

Boston's overall offense under Walker is also nearly identical to what it was under Irving, per NBA.com.

  • 2018-19 Celtics: 111.3 offensive rating
  • 2019-20 Celtics: 111.5 offensive rating

A few notable statistical differences between Kyrie of last season and Kemba of this season: Kemba is shooting 39 percent from 3 (en route to career-high effective field-goal percentage), while Kyrie shot 34 percent from deep last season. Also, Kemba is only shooting 16 times per game this season, while Kyrie shot over 18 times per game in his last season with Boston. 

But again, don't pay too much attention to the stats. Go one season back, and Kyrie shot 40 percent from 3 in his first year with the Celtics and was so smitten with the organization that he declared his long-term allegiance before Year Two even started. That didn't work out so well. 

For Walker, it's only the halfway point of Year One. A lot can change, especially if the Celtics underwhelm in the playoffs. But for now, this team undeniably feels different. And in the end, if two players are going to be virtually identical from a statistical standpoint, it becomes pretty difficult not to prefer the one who makes you smile. but it does forecast a difficult road ahead. 

Jaylen and Jayson: A-

If we're going to nitpick, Tatum's 49.5 effective field-goal percentage is the lowest of his career, per Cleaning the Glass, and Brown has had a pretty awful start to his January on the offensive end, particularly the closer he gets to the basket (just 41 percent at the rim and 40 percent from inside nine feet, per NBA.com). Tatum has had trouble finishing consistently all season; he's shooting 56 percent at the rim, which ranks in the 29th percentile among players at his position, per Cleaning the Glass. 

That's about all the negative I can muster about these two guys, both of which, in my opinion, belong in the All-Star Game. I don't think they'll both get in. I think Tatum will, but my bet is Brown gets snubbed. It's a shame, because Brown is having a stellar season. His 119.4 points per 100 shots attempts is the most efficient scoring mark of his career, per Cleaning the Glass. He's shooting 40 percent from 3 with a 56.5 EFG -- both also career highs, per CTG. 

Brown is also registering a career-high usage rate. This is part of the Kemba effect. Boston's offense allows for any one of Walker, Tatum, Brown, Smart and/or Gordon Hayward to serve as the primary playmaker/pick-and-roll initiator on any given possession. And when Brown isn't initiating, he's always ready to shoot and/or attack off the catch. Per Synergy, he ranks in the 81st percentile in spot-up scoring situations, and he's slowly continuing to improve as a passer when he puts the ball on the floor. 

Brown's shot looks so pure this season. Confident. My only beefs are when he's on the left wing or in the corner, he sometimes drifts toward the baseline when he catches a swing pass and goes right into a shot, rather than squaring up when he has time. And I also wish he would attack all the way to the rim with a bit more explosion in the half court (rather than mostly keeping the same pace from his dribble into his shot, which can be good in some instances, but sometimes leads to him finishing gingerly). 

Brown ranks in the 95th percentile for defensive rebounding percentage among players at his position, per Cleaning the Glass, and that's a huge weapon as he can turn those rebounds -- or quick outlet passes -- into coast-to-coast finishes with his speed.  

As for Tatum, there is just no way you can watch this guy and not think he's special. His game is so smooth. His jumper so pure. His handle and footwork so tight. Seriously, the guy has Kobe Bryant feet, and I do not say that lightly. Look at the up-and-under, the drop step, and the reverse pivot into a seamless spin and fade-away jumper. 

Yes, I know the shooting percentages are down, particularly at the rim, but Tatum is still shooting over 36 percent from 3 with far more responsibility as a scorer than he's ever had. His usage rate is the highest it's ever been, and his 21.6 points per game are up from 13.9 his rookie season and 15.7 last season. 

There's a similar thing happening with Jimmy Butler in Miami in that his shooting percentages have been down -- career lows, in fact -- for much of the season, and yet his impact is undeniable. Butler ranks seventh in ESPN's Real Plus-Minus. Tatum is 12th. Much of that is due to his defense, which has been All-NBA fantastic this season. 

"That's where he's really made a jump," an Eastern Conference scout told CBS Sports. "Scoring is natural for him. But there were some questions about his defense coming out [of Duke]; I think he probably just didn't always commit to playing [defense], like a lot of teenagers who can score the ball so easily. But he's always had that length and he's a great athlete. He's got everything you need to be an elite defender, and he's just starting to put it together. You can tell he's really starting to read the game."

Watch here as 6-foot Kemba Walker gets switched onto 6-10 Ben Simmons in the post, but before an entry pass can be made Tatum is already recognizing the situation and coming from the weak side:

Tatum is top 25 in steals per game, and as illustrated in the clip above, he's become so good off the ball in particular. He's always in a stance, never standing around. His head is on a swivel. Watch on the play below how he keeps track of the ball and his man in the corner, reversing his stance mid-action to see both, before ultimately closing out to a shooter (that isn't even his man) from about 15 feet away.

In today's game of drive-and-kick basketball, one of the hardest decisions to make as a defender is when to help down on the penetrator and when to stay with the shooter. Tatum can do both. Watch here as he slides down just enough to cut off a driver, only to anticipate the kick-out in time to jump the passing lane and go streaking the other way. 

Working together as long, versatile wings, Brown and Tatum are a defensive coach's dream, and an opposing coach's nightmare. This next possession should be put in the defensive Smithsonian -- Brown making Kris Dunn's life a living hell on the ball, Tatum hyper-aware off the ball and having the instincts and length to rush to block a 3-point shot from a 7-footer in the corner. 

Having Tatum and Brown, at 21 and 23 years old respectively, is a gold mine. Ainge is a genius for rating Tatum as the best player in the highly touted 2018 draft class and for not trading Brown when he had so many opportunities to do so. They are stars. Both of them. Throw in Marcus Smart and Gordon Hayward, and the Celtics can switch anything on the perimeter, and they have the collective length to trap and double and gamble for steals without compromising their collective ability to help one another out and recover to shooters. 

There's a reason the Celtics have the No. 4 defense in the league. 

Center by committee: B

Boston's biggest offseason departure wasn't Kyrie Irving. It was Al Horford. The most common qualification you'll hear with regard to the Celtics' one-piece-away championship potential is "they need a big man." It's true, they don't have an All-Star-level center, and they surely don't have anyone who can do the things Horford did as an offensive hub and legit 3-point shooter. 

That said, Daniel Theis, Enes Kanter and Robert Williams (before he got hurt), have been pretty darn good by committee. Through Monday, players are shooting just 58.7 percent in the restricted area against Theis, per NBA.com. That's better than Defensive Player of the Year favorite Anthony Davis (58.8), and much better than the likes of Joel Embiid, Rudy Gobert, and yes, Horford. 

Theis' block percentage ranks in the 85th percentile, per Cleaning the Glass -- while Williams, a supercharged athlete, ranks in the 93rd percentile. Look at Williams doing work on this reel:

Kanter, meanwhile, continues to be a rebounding machine and a walking low-post bucket when you try to put an even halfway inferior defender on him, as Chicago found out earlier this season. 

Kanter grabs 26.6 percent of all defensive rebounds available when he's on the court, and 16.1 percent of all offensive rebounds available. Those two marks put him in the 96th and 99th percentile, respectively. I understand Kanter's defensive limitations. He can be a matador in the paint. But the narrative that he's so bad defensively that he's unplayable in the playoffs is ridiculous. He was arguably the third-most important playoff player on a Portland Trail Blazers team that went to the conference finals last season. 

Kanter gets you so many extra possessions. You can't play him huge minutes, but for stretches he can flat-out carry a team as a dominant -- yes, dominant -- one-on-one post scorer and relentless offensive rebounder. Per ESPN's Real Plus-Minus, Kanter is the 32nd most impactful player in the league this season independent of the circumstances around him, 30 spots ahead of Horford entering play on Tuesday. 

That stat isn't perfect. Horford is in a weird situation in Philadelphia, while he fit like a glove in Boston. And it's not to suggest Kanter is in any way a better player than Horford. But he's clearly playing good, impactful basketball, and the Celtics have so much defensive cover for him on the perimeter, even the things he doesn't do well is manageable on this team. 

In fact, when Boston plays Kanter with Walker, Tatum, Brown and Smart, the Celtics are plus-21 per 100 possessions for the season with a 97.5 defensive rating, per Cleaning the Glass. 

That said, the question does remain whether these three guys can hold up against a truly elite center like Joel Embiid in a playoff series, and we know none of them can serve as a halfway viable defender on Giannis Antetokounmpo the way Horford could. Ainge may still try to make a deadline move for a big man. We've heard rumors about Andre Drummond. 

But for now, these three are holding down the fort in a more than acceptable way. 

Overall Grade: A-

At the end of the day, the Celtics are the No. 2 team in the East with a 27-11 record and the No. 3 net rating in the league. They're No. 4 in defense, No. 5 in offense, and one of three teams to be top five in both. Kemba Walker and Jayson Tatum are All-Star locks. Brown should be in there. Stevens will get Coach of the Year votes at this rate. 

Gordon Hayward was playing fantastic before he broke his hand, and he's starting to round back into form again. Marcus Smart is a legit Defensive Player of the Year candidate. The bench is short on offense, but the defense is stout with Brad Wanamaker, Semi Ojeleye and Grant Williams, and the lack of scoring can be mitigated by Boston's wealth of starter-level wings. 

At any point in time, any combination of Brown, Tatum and/or Hayward can lead the second unit. For the playoffs, the Celtics might even consider bringing Hayward off the bench for that very reason. 

All things considered, ask yourself: How much better could this season be going? The only team better in the Eastern Conference than Boston is the Milwaukee Bucks. I think they can get a little stagnant offensively. Tatum can be streaky. The bench, as mentioned, is thin on offense. And they haven't played particularly well of late (6-4 in their last 10). But those are nitpicks -- enough to put a minus behind Boston's A grade, but nothing more than that.