As the horrifying extent of Gordon Hayward’s injury became clear, Boston Celtics fans around the globe dropped their heads in disappointment. They’d witnessed the acquisition of two all-star-caliber players and a tantalizing rookie prospect over the off-season, but their 2017/18 season was in tatters just five minutes after it started. Almost a month later they’re sitting at 9-2, boasting the best record in the NBA. So, how have they done it?

Boston Celtics -- the league’s best defense?

This is certainly not a question many people would have been expecting to ask this year.

Last season, the Boston Celtics were average defensively. Not bad, but very much average, as they conceded 105.3 Points Per Game to sit right in the middle of the league in this category.

Over the off-season, two of their best defenders in Avery Bradley and Jae Crowder were traded away, causing many to question whether they would be able to compete at this end of the floor. Rather than just compete, though, Boston has improved to the point where they boast the league’s stingiest defense 11 games into the season.

Kyrie Irving has proven a revelation on this end of the floor, after a career in Cleveland which saw his defensive effort questioned on a regular basis. While he still isn’t outstanding, he has improved dramatically, playing a low-risk form of defense which was previously missing from his game.

Jaylen Brown and Jayson Tatum are both at an age which often goes hand-in-hand with poor defense, but their length has added an extra dimension to the Celtics' defense which was lacking last year. This size across the floor enables them to switch match-ups with ease, and cover space better than ever.

Kyrie Irving -- leader of the Celtics

Boasting probably the league’s best handles, as well as an elite shooting touch, no one has ever doubted Kyrie Irving’s talent. Many did, however, question whether he could successfully lead the Boston Celtics, playing for the first time outside the shadow of LeBron James.

He’s emphatically proved his doubters wrong, starting the season in some serious form.

His stats are nice without being jaw-dropping -- he’s averaging 22.3 points per game, just under 6 assists, and a couple of steals -- but what is most impressive is his maturity. He has developed from an offensive weapon capable of scoring on any given possession, to a reliable point guard who values making the right play over the most exciting one. His basic stats fail to mention the intangibles -- those times where he makes the right pass, even if it doesn’t result directly in an assist, or when he sacrifices his own scoring game to get his young teammates involved. These factors are more impressive than stats, and are a major reason for the Boston Celtics' early success.

Boston Celtics' star rookies

Tatum and Brown. Jayson and Jaylen. These two have been a revelation, becoming legitimately good players on what is currently the best team in the NBA. At just 19 years of age, Tatum is averaging over 14 points (while shooting 50% from the floor), six boards, nearly two assists, and almost a steal and a block per game. His partner in crime in Jaylen Brown shares similar numbers, with just over 15 points per game, over six boards, and nearly a steal in 31.5 minutes per game. It was rightly debated whether two players as young as these guys could play their role as starters on a good team. They have done so with aplomb, becoming vital members of a very good line up.

For the moment, the Boston Celtics are proving impossible to beat.

Whether they can keep this form going over a very long 82 game season is debatable, but if they stick to their current defensive principles and retain their evenness across the floor, they will continue to be a daunting prospect -- for every team in the league.