Here’s an odd fact about a league with more young stars than it’s had in decades: Other than Boston, the NBA’s four common-sense title favorites double as the four oldest teams by average age, weighted by minutes played. In descending order of age, they are: Cleveland, San Antonio, Houston, and Golden State.

On second thought, though, maybe that fact isn’t such a great surprise. The Cavaliers, Spurs, and Warriors have been entrenched as title favorites for several years now, their best players aging alongside one another, and their newest peer in Houston took a leap while completing the roster with a group of veteran additions: Luc Mbah a Moute (in his age-31 season) and Chris Paul, P.J. Tucker, and Gerald Green (all age-32).

Then there’s Boston, currently the East’s top seed with a 33–10 record, as a gerontological outlier. The Celtics are one of the league’s youngest teams, as only the lottery-bound Lakers and Suns boast lower average ages than Boston’s 24.5; not a single Celtic is older than Cleveland’s average age.

The Celtics aren’t just an anomaly this season, though; as a team this young and competitive, they’re a historical aberration as well. Before this season, 142 teams since the advent of the shot clock played with a weighted average age younger than 25, and they were generally awful, finishing with an average .365 winning percentage, which translates to a 30–52 record.

Few were anywhere near as good as these Celtics, with only 21 of those 142 teams finishing with a winning record, and only four winning at least 50 games: Milwaukee with 56 in 1969–70, Kareem Abdul-Jabbar’s rookie season; Portland with 54 in 2008–09, Brandon Roy’s peak; and Oklahoma City with 50 in 2009–10 and 55 in 2010–11, pre–James Harden trade. For comparison, as many teams in the sample earned 50-plus wins as 70-plus losses (or its winning-percentage equivalent, in the case of 7–59 Charlotte from the recent lockout year).

More than halfway through this season, the Celtics are on pace for 63 wins; even if they falter, they could lose more games than they win the rest of the year and still reach 50. Depending on how strongly one weighs regular-season versus playoff performance — those Abdul-Jabbar Bucks won a title, as did the equally young, 49–33 Trail Blazers in the 1976–77 season — it’s not a stretch to argue that these Celtics could finish as the best young team in league history.

Several factors interact to produce this potentially unprecedented result. An outlier team starts with an outlier player, and the Celtics’ youngest, 19-year-old Jayson Tatum, has played with the panache of a seasoned veteran. The no. 3 pick in the 2017 draft looks like he’s been scooting by NBA defenders for years, and he’s shattering teenage efficiency records, with a 62.6 percent true-shooting mark that’s more than 5 percentage points better than every other qualified teen in league history. Tatum isn’t a perfect player — look at his ratio of 57 assists to 54 turnovers — but it’s hard to imagine a smoother start to his NBA career. He’s in the 98th percentile in points per possession as a pick-and-roll ball handler, and his shooting exploits have exceeded all reasonable expectations. After ranking fifth on his own college team in 3-point percentage (34.2) last year, he ranks fourth in the NBA in long-range accuracy (46.2) halfway through this season.

His predecessor as the no. 3 overall pick, teammate Jaylen Brown, is 21 years old and producing nearly identical per-game totals to Tatum. Tatum averages 13.9 points, 5.5 rebounds, and 1.3 assists each night in 31.1 minutes; Brown averages 14.1 points, 5.7 rebounds, 1.3 assists, and 31.3 minutes. The sophomore wing has managed the tricky double of increasing his efficiency and usage rate in tandem, and his stalwart involvement on both offense and defense has helped fill the void left by Gordon Hayward since the prized summer signee broke his leg and dislocated his ankle five minutes into the season.

Boston likely wouldn’t place on the under-25 list at all were it not for the 27-year-old Hayward’s injury, which has led to more playing time for the likes of Brown (whose minutes per game have nearly doubled from his rookie year) and Semi Ojeleye, the team’s 23-year-old rookie forward. Boston would prefer to have one of its best players on the court, and the Celtics’ postseason ceiling remains lower with Hayward out. But his absence has unlocked experimental lineup opportunities for coach Brad Stevens, who has found intriguing combinations including Tatum and Brown at the wings and Al Horford and Aron Baynes in the frontcourt.

It helps Boston’s largely young roster that the minimally staffed old guard is playing well. Boston’s oldest player, the 31-year-old Horford, is the fulcrum upon which all of Stevens’s stratagems turn, and the team’s net rating is 7.3 ticks higher with its versatile big man on the floor, the best mark for any Celtics rotation player. Second on that team leaderboard (plus-6.7) is the second-oldest player, the 31-year-old Baynes, who has the best individual defensive rating of any rotation player in the league, per NBA.com, and is second in ESPN’s defensive real-plus minus metric.

In general, Boston’s defense represents another outlier for a young team. Per Basketball-Reference, the Celtics’ team defensive rating is 6.2 points per 100 possessions better than the league average, which would best the 1997–98 Cavaliers’ record of 5.9 ticks for the largest difference for an under-25 team. (Basketball-Reference’s rating data extends back to the 1973–74 season.) It’s not only the 30-something bigs who are leading the charge, either; while individual defensive statistics are difficult to disentangle, Brown and Tatum rank fifth and seventh, respectively, at their positions by defensive real plus-minus, and opponents score less than a point per possession when the two wings share the floor.

All six @jaytatum0 rejections in one clip for your pleasure! pic.twitter.com/aLYS7LejwS — Tomek Kordylewski (@Timi_093) January 7, 2018

Beyond the starting lineup, the Celtics defense remains staunch, and it’s this segment of the roster that most noticeably separates Boston from its contending peers. While other title favorites bolstered their benches with veterans — the aforementioned 30-somethings in Houston; Nick Young in Golden State; the likes of Dwyane Wade, Jose Calderon, and Jeff Green in Cleveland — the Celtics veered younger. Marcus Morris is Boston’s only bench player older than 25; for comparison, no Cavalier playing at least 10 minutes per game is 25 or younger, meaning that former Cav and present Celtic Kyrie Irving, who’s a veteran in Boston, would somehow be Cleveland’s youngest rotation player.

Much of that approach is purely opportunistic, as various trades gave Boston eight first-round picks in the last four drafts. That depth provided sufficient surplus that the team could absorb whiffs on some selections — James Young (no. 17 in the 2014 draft), R.J. Hunter (no. 28 in 2015) — and still be able to fill out a bench with talent, via the likes of backup guards Marcus Smart (no. 6 in 2014) and Terry Rozier (no. 16 in 2015). It’s also logistical: Between all those first-rounders and Boston’s maximum contract free agents, there’s little room left on the roster for veteran additions.

Lastly, it’s forward-looking: When constructing his depth chart, Boston roster architect Danny Ainge understood that the East will remain LeBron James’s dominion for as long as he stays in the conference, so a roster revamp would necessarily have to target a future more distant than executives typically consider. Rosters usually navigate a trade-off between present contention and future potential, but the Celtics straddle both lanes because their best players do, too.

A single trade netted Boston the picks that eventually helped bring in Irving, Brown, and Tatum, with one more juicy selection — possibly one in the 2–5 range next June, via the Lakers — still to come. It bears repeating that Irving is 25, Brown 21, Tatum 19, and the next member they draft into their young core is in all likelihood another teenager, still in college. (On Wednesday, The Ringer’s NBA draftniks projected galactic Arizona center Deandre Ayton, currently a 19-year-old college freshman, to Boston.) No team is better positioned to take advantage of the post-LeBron era — if it ever comes — in the Eastern Conference.

But Boston is positioned to make a run this year, too, and in the near future. Next season, Horford, Hayward, and Irving will combine to make $80.2 million, leaving just $20 or so million for the rest of the roster before the Celtics surpass the salary cap. Tatum and Brown will combine to command just $11.9 million, though — less than the Pelicans’ Solomon Hill, who has averaged 6.4 career points per game, will by himself — leaving Ainge plenty of flexibility to surround his core with talented depth pieces. He might even bring in a veteran or two to add some shot-making zest off the bench or provide a more traditional point guard to back up Irving.

At that point, with potential older additions and each of the team’s current players aging a year, Boston would no longer appear on the under-25 list. The roster would be properly middle-aged, at least in NBA terms, with a healthy mix of pre-prime players on rookie contracts and the vibrant, well-paid Big 3 of Irving, Hayward, and Horford. The Celtics would no longer be an anomaly — but as this season’s Warriors et al. have shown, that kind of growth and balance befit a favorite.