One week from Tuesday, the Celtics will begin training camp without Jaylen Brown on their roster for the first time since 2015.

Brown’s blockbuster trade to Philadelphia defined a franchise-shaking offseason for Boston, which revamped the top of its roster by breaking up one of the NBA’s most successful duos.

With the longtime cornerstone now suiting up for the rival 76ers, the Celtics will push ahead with Jayson Tatum surrounded by a new supporting cast. That group — headlined by veteran newcomers Paul George and Mitchell Robinson and championship-winning holdovers like Derrick White and Payton Pritchard — will look to return the C’s to championship contention following their earliest playoff exit in five years.

Here are five Celtics players with the most to prove as the team enters its post-Jaylen era:

Paul George

The Celtics’ hopes of contending in a tough Eastern Conference this season could hinge on George, the 36-year-old, oft-injured, former All-NBA wing they acquired in the Brown trade (along with two future first-round picks and two seconds).

George proved during last season’s Celtics-76ers playoff series that he still can be an effective player when healthy. His defense, 3-point shooting, veteran savvy and willingness to play a supporting role should make him a good fit for Boston’s system. He said all the right things last week in his introductory news conference, sympathizing with fans who were put off by the trade and deferring to Tatum as the team’s “superstar.”

But none of that will matter if George, who’s missed nearly 40% of his teams’ games over the last seven seasons, can’t stay on the court. Expect the Celtics to manage the nine-time All-Star’s workload with the goal of having him fit and available for the postseason. They have the personnel to do so, as their entire stable of young, energetic wings is back this season.

Jayson Tatum

Tatum put up encouraging numbers after his March debut last season (21.8 points, 10.0 rebounds, 5.3 assists, 1.4 steals per game in 16 regular-season appearances) and was arguably Boston’s best player during the team’s brief playoff run.

But he was playing at, by his own estimation, “80% to 85%” of his full capacity after recovering from Achilles surgery, and a related knee issue prevented him from suiting up for the decisive Game 7, which the Celtics lost at home.

Now nearly 17 months removed from surgery, Tatum should be back to full strength as the new season tips off. But will he look like the same player he was before he crumpled to the court at Madison Square Garden last May? Will the team be more cautious with his minutes? And, health questions aside, how will Tatum’s game change without his career-long co-star?

Payton Pritchard

Who will replace Brown as the No. 2 option in Boston’s offense? It could be George, who was a perennial 20-plus-point-per-game scorer before taking on a lower-volume role in his two seasons with Philadelphia. Another candidate: Pritchard, who’s coming off back-to-back career years and was one of the NBA’s most efficient isolation scorers in 2025-26.

The 2024-25 Sixth Man of the Year diversified his shot selection last season, scaling back his 3-point volume and working more in the midrange. Despite often being the smallest player on the court, he was one of the league’s best at navigating traffic and creating space for short jumpers. Fifty-seven players attempted at least 200 non-rim field goals inside the paint, and only Kevin Durant and Nikola Jokic made theirs at a higher rate than Pritchard’s 55.9%.

Two of the Celtics’ most intriguing training camp storylines are Pritchard-centric: 1) Will he start? He did so for the first half of last season but moved back to the bench after the team traded Anfernee Simons. And 2) Will he sign a contract extension before the season?

Currently playing on arguably the NBA’s team-friendliest deal (a four-year, $30 million pact that runs through 2027-28), Pritchard becomes extension-eligible on Oct. 1. NBA salary cap rules limit how much the team can offer the 28-year-old, however, meaning he could earn himself a larger payday by waiting. Pritchard told NBC Sports Boston last month he’s in “no rush” to sign.

Derrick White

The veteran guard is beloved for his defense, dirty work and ability to, as head coach Joe Mazzulla often puts it, “impact winning.” Only Shai Gilgeous-Alexander, Victor Wembanyama and Chet Holmgren had a better overall plus/minus than White last season.

But White’s shooting was a persistent issue throughout the season — his career-worst 39.4% field-goal percentage ranked last among all NBA players with at least 750 shot attempts — and it became a full-blown crisis in the playoffs. He shot 32.1% from the field and 27.3% from three in the 76ers series, averaging a mere 8.7 points before going for 26 in Game 7.

Add in his age (32, third-oldest on the roster behind George and Mike Conley) and contract status (he’s owed more than $30 million in each of the next three seasons, including a player option for 2028-29), and it’s fair to wonder how much longer White will be wearing Celtics green. Boston will be hoping he can rediscover the touch he showed in his first three full seasons with the franchise, during which he made 38.7% of his 3-pointers.

Hugo Gonzalez

After last season, Brad Stevens said Gonzalez will be “a critical part of (the Celtics) moving forward.” A month later, Boston’s president of basketball operations doubled down on that statement by reportedly refusing to include the 2025 first-round draft pick (or 2024 first-rounder Baylor Scheierman) in the Celtics’ Brown-centric trade offer for Giannis Antetokounmpo. The Milwaukee Bucks wound up shipping Antetokounmpo to Miami instead.

It’s unclear whether offering Gonzalez would have been enough to land the two-time NBA MVP — and thus avoid the George-and-picks return that Boston settled for from Philly — but the choice not to dialed up the pressure on the 20-year-old Spaniard. He’ll be expected to show real growth this season after posting excellent advanced stats but modest production as a rookie (3.9 points, 3.3 rebounds per game) and falling out of Mazzulla’s rotation down the stretch.

After a solid showing at the Las Vegas Summer League, Gonzalez will compete for minutes with players like Scheierman, Jordan Walsh and Ron Harper Jr. in Year 2.