Do we really know how good the Boston Celtics are?

The Boston Celtics find themselves as the third seed in the Eastern Conference with the NBA suspended due to COVID-19, sporting the NBA’s fifth best winning percentage and point differential. The team’s presence among the league’s upper crust is far from unfathomable.

The Celtics sport four All-Star caliber players, including a trio of versatile wings in Jayson Tatum, Jaylen Brown, and Gordon Hayward that enable them to play with a dynamism and flexibility that is matched by only a handful of other outfits (just to be clear, the fourth player referenced here is All-Star starter Kemba Walker). Boston was always going to be good, but the degree to which they’ve excelled to date exceeds most reasonable expectations entering the year.

The Celtics, it was assumed, would only achieve true title contention if/when Tatum and Brown took development leaps sufficient to propel them there, a reality most believed to be at least a couple of years away. However, Boston’s precocious duo appears to have started to make that jump ahead of schedule.

Tatum became an All-Star and had begun an ascension towards superstardom prior to the suspension of the season. Brown tightened his game over the summer and assumed the role of a perfect complementary two-way force, efficient on offense across a variety of settings and terrifyingly malleable and athletic as a defender. The two paired with established stars in Walker and Hayward, and a dutiful and intelligent role player in Daniel Theis form an extremely formidable starting five with vets Marcus Smart and Enes Kanter and a handful of young up-and-comers in the second unit.

Photo by Barry Chin/The Boston Globe via Getty Images

The Celtics starters have outscored opponents by 14.3 points per 100 possessions in non-garbage-time minutes, per Cleaning the Glass, a major contribution to the teams overall 6.6 net rating, the number three mark in the NBA. That ranking actually might undersell just how good Boston really is.

The Celtics’ most used lineup - the same starting five highlighted above - has played a grand total of just 390 non-garbage-time possessions together. That’s less than any of the other team’s in the top four of either conference. For reference, the Milwaukee Bucks most commonly implemented lineup - Eric Bledsoe, Wes Matthews, Khris Middleton, Giannis Antetokounmpo, and Brook Lopez - has been on the court for 930 non-garbage-time possessions, roughly 2.4 times Boston’s starters.

The Celtics have been plagued with minor injuries for the majority of the season, and their team statistics have suffered accordingly. Whether or not the degree of undercounting really matters is open for debate. If the Celtics swapped out their aggregate average for possessions played by starters to align to a ratio in line with the Bucks (a shift from 6% to 14%) their net rating in non-garbage-time would jump to 7.1.

That’s not a monumental difference, but it would put them in a tie for second with the Los Angeles Lakers, and it’s illustrative of a broader point: Boston may have a higher ceiling than aggregate data suggests if it can reach the postseason with its core fully healthy.

There is some danger in this manner of thinking. Health matters, and to ignore the reason why the Celtics starters have played so few games together would be folly. There’s also the realities of the layoffs to consider. Every team plays its best units more frequently in the postseason, and Boston’s best aren’t so good as to outpace their peers.

Milwaukee’s starting five, for example has a non-garbage-time net rating of 19.4, a level of effectiveness that far exceeds any lineups that the Celtics have implemented that have played any meaningful amount of possessions. The Bucks’ units with Antetokounmpo at center have pushed that mark up to a truly ludicrous 21.7.

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But Milwaukee is an extreme example. No one can touch them from a net rating perspective this year. However, Boston’s best lineups perform at a level similar to the most effective options of all non-Bucks contenders, and in that there is plenty of reason for optimism. The Celtics have the statistical profile of a title contender, and a depth of talent that is significant enough to make one wonder if they can overcome the lack of a clear cut top-10 talent.

Boston has been very good this year, and its ceiling may be a touch higher than its record and net rating suggest. Even still, the Celtics probably only have a puncher’s chance at making real noise in the post-season (whatever that looks like). That’s nothing to sneeze at. You need to be exceptional to have even a sliver of hope at the game’s highest level.