Up stepped Kyrie.

To begin this season, Irving was playing possibly the best basketball of his career. Considering this is an NBA title-winning guard who led his team in clutch situations in those NBA Finals, this is quite the the achievement. Irving's raw numbers are slightly down on last year, down to 24.1 points and 5.0 assists per game from 25.2 and 5.8 last year, but his scoring efficiency is up, his per-36 numbers are up, and his passing efficiency is up.

Up, too, stepped Jayson Tatum. Given Hayward's starting spot, Tatum has looked incredibly assured despite only playing 43 NBA games and one year of college basketball. He is poised beyond his years on both ends of the floor, among the league leaders in three-point shooting and also standing out defensively. Tatum is shooting 46.2% from three-point range, at one time leading the league in percentage, and has a 62.6% true shooting percentage, 38th in the league and 7th among all players with at least 500 points scored. Defensively, Tatum averages as-near-as-is a block and a steal per game, and has a 101 defensive rating that is even better than his team's leading mark. He really was the windfall in the draft that was hoped for for so long.

It is true and fair to say that the depth and quality throughout the team is a major reason why Boston has been able to not just stay afloat but thrive, and Tatum's quick progression is the embodiment of that. But, primarily, the early season play of Kyrie Irving that, even without Hayward, is why the Celtics have risen to the top of the East anyway.

In 15 November games, Kyrie recorded 24.1 points and 4.9 assists per game, shooting 50.0% from the floor, and with a 62.1% true shooting percentage overall. He was shooting as efficiently as Tatum while taking infinitely tougher shots, and shifting the defence around enough to create the space for Tatum and the other finishers to capitalise upon. Irving passed better, too, recording a 30.0% assist rate (his best in four years) alongside a career-low 10.0% turnover percentage, and stopping the ball less than he ever did in Cleveland.

Furthermore, to begin the season, Kyrie was playing the best defence of his career. The Celtics lead the league with a 101.9 defensive rating, and Kyrie is a part of that, sporting a 104 rating of his own (a measure of his team's defence with him on the floor) that is middle of the-pack among the team's rotation. The 'best' defence of Irving's career was still average, but average will do, and his defensive effort had picked up, which often can be enough on its own.

It must, however, sustain. Fuelled by Irving's offence, the Celtics peeled off a 16-game winning streak to rise to the top of the East, a streak in which they were leading the league in defensive rebounding and playing incredible defence all of the court. They stopped the ball and then they got it back. But of late, they have wobbled in these areas. And Kyrie is again partly why.

Kyrie's defence is still prone to lapsing, particularly so since the start of December as opposing coaches have learned to counter Stevens's best attempts to hide him, and some opposing guards are going off. Amid an otherwise down year, Utah Jazz point guard Ricky Rubio was able to score a season-high 22 points versus the Celtics, taking advantage of Irving's tendency to still run completely the wrong way, especially when a screen is involved.

If Kyrie is to lead this team as far as they can go, the leadership is required on both ends. He does not need to have Chris Paul's instincts, Tyus Jones's hands or Josh Richardson's versatility to be effective on that end. He just needs to try, and, should he get beat, try and recover. It does make a difference, as evidenced since the ending of the streak, since when he has tried a bit less.

Nevertheless, imperfections on one end do not diminish his impact on the other. Whether or not he should have to, what Kyrie gives up, he can more than get back.

In the absence of Hayward, Kyrie is the one Celtic who can consistently create a high-percentage shot for himself. Horford is an excellent passer, the consummate high-IQ team player who can score from all ranges now that he has developed a high-efficiency three-point stroke, but he is more of a passer and finisher than a creator. He can hit all cutters, but those cutters need the space opened up by the threat of dribble penetration and outside shooting. The same is true for Tatum and his wing partner Jaylen Brown, and while Marcus Smart and Terry Rozier are bulldogs in their own way, neither can consistently break down or shift a defensively offensively.

Kyrie's important to the Celtics lies in the fact that he can do things on the court that none of his team mates can do, to a standard that almost no one else in the league can rival. His ball-handling, shot creation and ability to hit tough shots are among the league's all-time best, and have already won him one title. Al Horford may lead the team in assists, but it is Kyrie getting the ball up, finding him in pick-and-roll action and cutting off of him.

With no LeBron James there to bail him out, Irving still needs to commit to playing an all-around game in order to maximise the talents of both himself and his team. Going to a team built on depth and The Butler Way, in which every player has the opportunity to score and pass, may be the purifying change Irving needed. Tyronn Lue and the Cavaliers' brain trust no doubt preached the same mantras, but they hadn't the personnel to implement them.

For the most part, Kyrie has done that. And if he can get back to playing the basketball he did six weeks ago, the East is theirs.