What's next for the star, the Celtics and the future

Testing on Tuesday confirmed what anyone who saw Jayson Tatum fall to the floor during Monday's Boston Celtics loss to the New York Knicks already feared: Tatum suffered a rupture of his right Achilles tendon late in the fourth quarter, sidelining him not only for the remainder of this postseason but also jeopardizing his availability for the 2025-26 season.

Given Tatum's importance to the defending champions, as their leading scorer and a three-time All-NBA first team pick (with a fourth likely on the way when this year's teams are announced soon), his injury is one of the most consequential in NBA history.

The ramifications start with Boston's ability to come back from a 3-1 deficit against the Knicks, who are now favored in this series, but go well beyond that to how the Celtics will handle next season.

Let's look at how Boston might play without Tatum, plus the history of Achilles injuries in the NBA and its implications for the Celtics.

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Jayson Tatum helped off court after going down in pain

Celtics star Jayson Tatum leaves the game after an injury in the fourth quarter vs. the Knicks.

When might we see Tatum return?

No NBA player since Jose Juan Barea in 2019 has returned sooner than 10½ months after an Achilles rupture, suggesting the Celtics should plan on Tatum missing the entire 2025-26 regular season. A postseason return is more realistic, but there's basically no precedent for that.

The only NBA player I could find who returned from a seasonlong injury in the playoffs was Larry Krystkowiak with the Milwaukee Bucks in 1991, when he came back from an ACL repair to play three games and total two points. Although Krystkowiak was a starter before the injury, the stakes weren't quite the same as with an All-NBA first teamer.

Postseason returns were discussed when both Kevin Durant and Klay Thompson suffered injuries in the 2019 NBA Finals, but neither came to pass. The Golden State Warriors' 2019-20 season was long over by the time Thompson was cleared -- he later suffered a subsequent Achilles rupture in a pickup game that offseason. Durant, meanwhile, opted not to join the Brooklyn Nets for the bubble restart in the summer of 2020 and returned a year and a half after his Achilles rupture at the start of the 2020-21 campaign.

Based on that history, Boston might want to approach 2025-26 as if Tatum won't play at all, even in the playoffs. That dramatically changes the thinking for a team that has won 15 playoff series in the seven years since drafting Tatum No. 3 in 2018.

Second-apron squeeze

As ESPN's Brian Windhorst recently detailed, the Celtics are entering a precarious financial situation. With Tatum's supermax extension -- the largest in NBA history to date, supplanting teammate Jaylen Brown's -- scheduled to kick in next summer, Boston is more than $40 million over the 2025-26 luxury tax line. That doesn't count veteran stalwart Al Horford, who will be an unrestricted free agent at age 39.

The looming tax bill for the Celtics, plus restrictions on teams that exceed the second luxury tax apron, always figured to force difficult decisions. Tatum's injury accelerates them. After all, paying well north of $200 million in luxury taxes for a potential championship team is one thing. Doing so for a team whose ability to advance is uncertain is another.

Age is another consideration. If Boston's next title window shifts from 2026 to 2027, that affects the thinking about veteran players, most notably Jrue Holiday. By the 2026-27 season, Holiday will be 36 years old. The Celtics might be better off sending Holiday to another contender while his value remains strong in a move that could both reduce their payroll and get them younger on the perimeter at the cost of downgrading defensively.

Conversely, Tatum's absence could prevent Boston from considering the nuclear option of trading Brown. The long-term financial challenge for the Celtics is having two players in Brown and Tatum who combined make more than 60% of the salary cap through 2028-29. It's not going to be possible for Boston to maintain the depth that has been a hallmark now that its two most important players are getting paid like the stars they are.

In Tatum's absence, however, Brown's ability to create his own shots will become paramount. They were the lone two Celtics rotation players to be assisted on less than 59% of their field goals this season --Tatum at 39% and Brown at 46%.

Expectations for Tatum

Durant's return will undoubtedly be the comparison for Tatum. Despite suffering his Achilles injury at 30, three years older than Tatum, Durant returned as the dominant force he was before the injury and remains an All-Star six years removed from it.

The example of Durant shows it's possible to avoid a major loss of performance after an Achilles rupture. Perhaps the most likely impact for Tatum will be compromising his durability. Including the playoffs, no one has played more NBA games than Tatum since he was drafted, and this season's eight games missed due to injury -- six of them in March and April, with Boston coasting to the No. 2 seed -- were a career high.

Whenever Tatum is back on the court, he'll presumably be limited from playing back-to-back games for a period of time and will probably have his minutes monitored as well. That could make it difficult for Tatum to add more All-NBA first-team appearances, even if his productivity does not suffer.

Typically, multiskilled wings have performed the best coming back from Achilles injuries. Beyond Durant, that group includes Thompson and Wesley Matthews, who was back on the court less than eight months after his injury in 2015 and continued to play in the NBA through age 37.

There's no guarantee Tatum will join that group, rather than join more cautionary examples like DeMarcus Cousins and John Wall. But there's also no reason to consider an Achilles rupture the end of Tatum's ability to play at a high level.

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Stephen A.: Knicks should beat Celtics without Tatum

Stephen A. Smith believes the Knicks will overcome the Celtics in the Eastern Conference semifinals should Jayson Tatum be ruled out due to injury.

How can the Celtics come back in this series?

First, they need to overcome the shock of seeing their star player helped to the locker room in a wheelchair. Tatum's injury was disheartening, but his Boston teammates will have a couple of days to process it by the time the team tries to stay alive in Game 5 at home on Wednesday night.

Even before Tatum's injury, the Celtics were in a huge hole after falling down 3-1 in the series. Historically, 3-1 comebacks have been much more feasible for the higher seed, as Boston is. Still, that means teams have rallied to win 8% of the time in best-of-seven series since 1984 (going 5-58), compared with just 1% of the time in series where the lower seed trails 3-1 (2-141).

Beyond that, Tatum was the biggest reason the Celtics were in Game 4 despite giving up 70 points in the second half. Tatum scored 42 points in 40 minutes, tying the most career 40-point playoff games for any Boston player, before going down.

In Tatum's absence, the Celtics will need to rely on a defense that held the Knicks to a combined 184 points in Games 2 and 3. Keeping Jalen Brunson out of the paint should be the top priority. Brunson's 18 points in the paint on Monday nearly matched his total of 22 over the first three games of the series.

As a team, New York had 64 points in the paint in Game 4, the third most by a team in any playoff game this season, according to NBA Advanced Stats. The Celtics could replace Tatum by putting more size on the court, protecting the rim at the expense of their own shooting. If Boston can get the Knicks' offense back in the mud, there's enough scoring for the Celtics to win three consecutive games and pull off an improbable comeback.

Nonetheless, the combination of losing the game and Tatum on Monday has taken Boston from having the best odds to win the Eastern Conference at ESPN BET entering Game 4 to last of the four remaining teams now.