The Boston Celtics suffered a historic playoff defeat, losing a 3-1 series lead to the Philadelphia 76ers in the first round of the 2026 NBA Playoffs. This marks the worst series loss in Celtics franchise history.
May 2, 2026; Boston, Massachusetts, USA; Philadelphia 76ers guard Kelly Oubre Jr. (9) dunks past Boston Celtics center Luka Garza (52) during the first quarter of game seven of the first round of the 2026 NBA Playoffs at TD Garden.
The Boston Celtics have been in the NBA since the leagueâs inception in 1949. Even with over 70 years on the court, the Celticsâ blown 3-1 lead and eventual loss to the Philadelphia 76ers in the first round stands as the worst series defeat in franchise history.
Here are some numbers to explain why.
First and foremost, this kind of playoff defeat is rare for the Boston Celtics franchise.
Before the 2026 NBA playoffs, there were just five times Boston lost in the first round as the higher seed. The last of those instances happened in 1993. It also occurred in 1951, 1952, 1956, and 1990.
In 1990 and 1993, Boston entered the playoffs as the No. 4 seed and lost to the No. 5 seed. During the fifties, the Celtics were the No. 2 seed and fell to the No. 3 seed.
After decades without repeating the result, that changed in 2026. The two-seeded Celtics lost to the seven-seeded Sixers. It marked the first time in franchise history that Boston lost in the first round as a top-three seed since the NBA playoff field expanded to eight teams per conference in 1983-84.
The Boston Celtics lost a 3-1 series lead to the Philadelphia 76ers, resulting in their elimination in the first round of the 2026 NBA Playoffs.
This loss is significant as it represents the worst series defeat in Boston Celtics franchise history, highlighting a rare failure for a historically successful team.
The Boston Celtics have been in the NBA since its inception in 1949, making them one of the league's oldest franchises.
Losing a 3-1 playoff lead could lead to significant changes in the Celtics' roster and strategy as they assess their performance and future prospects.
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The Celtics were not viewed as underdogs at any point in the series. In fact, quite the opposite.
Entering the postseason, Boston owned the best odds of any East team to win the 2026 championship at +550, according to bet365. The Sixers were at +17,500, ranking seventh in just the conference.
Itâs clear this was the worst first-round loss in Celticsâ history, but how does it compare to defeats in later rounds?
There have been 12 times in franchise history that the Celtics lost in the Eastern Conference Semifinals or Finals as the higher seed.
Among these instances, the most notable losses came in 2009, 2020, 2023, and 2025. Hereâs what happened in each of those series.
In 2009, Boston entered the playoffs coming off a championship. But the team played without superstar Kevin Garnett because of injury. Without the Hall of Famer, the second-seeded Celtics lost in seven to the third-seeded Orlando Magic.
Fast forward a decade, and Boston was the two-seed facing the fifth-seeded Miami Heat in the 2020 playoffs. Miami defeated Boston in six games in the ECF. That said, the Heat entered the series on a dominant run in the NBA Bubble with an 8-1 playoff record, including a series win over the top-seeded Milwaukee Bucks.
The Celtics and Heat would meet again in the ECF three seasons later. Eighth-seeded Miami jumped out to a 3-0 lead over two-seeded Boston. The Celtics rallied to force a Game 7, which Boston ultimately lost. Although it remains the only time the Celtics have lost to an eighth seed, Miami had already established itself as one of the hottest teams in the playoffs with three straight series upsets over other teams in the East.
The 2025 season appeared set up for another Celticsâ championship run. Boston entered the Eastern Conference Semifinals as the No. 2 seed against the third-seeded New York Knicks. When Jayson Tatum tore his Achilles tendon in Game 4, the Celtics were already trailing and minutes away from falling behind 3-1.
The 2009 and 2025 teams both entered the season with championship expectations but lost to talented third-seeded opponents.
In 2020 and 2023, Boston may have been the higher seed, but Miami entered both conference finals playing elite basketball.
Compared to 2026, each of those losses is much more justifiable and an easier pill to swallow for Celtics fans.
Looking at the other side of the court, the Philadelphia 76ers experienced minimal recent playoff success before the 2026 postseason.
With Joel Embiid on its roster, Philadelphia had never advanced to the conference finals, unlike the opponents Boston faced in 2009, 2020, 2023, and 2025.
Philadelphia also entered the series without Embiid for the first three games, and still overcame a 3-1 deficit. Before 2026, the Celtics had never blown a 3-1 series lead in franchise history. Before the 2026 first round, it was 32-0 all-time when up 3-1.
When compared to the other painful playoff exits in Bostonâs history, none match what happened this year.
With both Tatum and Jaylen Brown still under 30, the Celtics now face major questions about their roster and how the team can avoid another collapse like this going forward.
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