In the 2021, ’22 and ’23 NBA Drafts, the Celtics drafted teenaged projects with the hopes of developing them into eventual NBA contributors.

This year, president of basketball operations Brad Stevens took a decidedly different approach.

A week after winning its 18th NBA title back in June, Boston added two uber-experienced college prospects to their championship core: Creighton wing Baylor Scheierman in the first round (No. 30 overall) and Gonzaga forward Anton Watson in the second (No. 54).

Scheierman and Watson both played five collegiate seasons, and both will be 24 years old by the time their rookie year tips off on Oct. 22. They’re 3 1/2 years older than last year’s Celtics draft pick, Jordan Walsh, who doesn’t turn 21 until March, and two years older than their 2022 draftee, the soon-to-be 22-year-old JD Davison.

“I think those guys both are winning players,” Stevens said on draft night. “They played in a lot of big moments and a lot of big games in big environments. They know how to play on both ends of the floor.”

Walsh and Davison both needed a great deal of G League seasoning to begin their pro careers, and neither looks ready to crack the Celtics’ regular rotation as the team reconvenes for training camp next week. Will things be different for Boston’s two new rookies, who combined for 313 appearances (227 starts) at the college level and should, in theory, be more prepared for the rigors of the NBA game? That’ll be one storyline to watch as the C’s begin their title defense.

Unfortunately for Scheierman and Watson, there simply won’t be an abundance of minutes to go around this season. The Celtics return nearly every player from their 2023-24 roster, including their entire postseason rotation.

In fact, Scheierman is the only official addition to that roster to date, with Watson signing a two-way deal that allows him to split time between the NBA club and Boston’s G League affiliate in Maine. Boston has one open 15-man roster spot, for which a group of non-roster players including veteran Lonnie Walker IV will compete in camp.

The Celtics did lose two reserves from last year’s squad, however – guard Svi Mykhailiuk, who signed with Utah, and forward Oshae Brissett, who remains a free agent – so there will be opportunities for Scheierman and/or Watson to carve out minor roles if they earn the trust of head coach Joe Mazzulla.

The 6-foot-6 Scheierman was best known for his 3-point shooting during his time at Creighton and South Dakota, but he’s also a skilled passer with great vision and is tenacious on the glass (his 9.0 defensive rebounds last season led the Big East). He’ll need to shoot the ball better than he did in the Las Vegas Summer League, during which he attempted 6.8 threes per game and made just 29.4% of them, but his greatest hurdle to clear will be on the defensive end, where NBA opponents will look to expose his relative lack of high-end athleticism.

“He’s always been super skilled, super smart and super tough,” said Stevens, who also worked out Scheierman ahead of the 2022 draft before he opted to stay in school. “He’s a basketball player now. He knows how to play. … He’s just got a lot of good things going for him.”

Watson, meanwhile, is a versatile defender whose game drew pre-draft comparisons to veteran Celtics big man Al Horford. He was not known as much of a perimeter shooter for Gonzaga (1.0 3-point attempts per game for his career; 1.5 last season), but the Celtics believe he has untapped potential in that area, as Horford did before adding it to his repertoire midway through his NBA career.

“Anton’s strength and ability to move his feet laterally give him a chance to be one of these big, strong hybrid forwards that can switch and guard a lot of people,” Stevens said. “I want him to come in here with the mindset that he’s going to let it fly like he’s never let it fly, because I think he’s a better shooter than he sometimes thinks he is.”

The 6-foot-8 Watson took that instruction to heart in his first games as a Celtic, averaging 4.0 threes per game (and shooting 35.0%) in five Summer League appearances. He enjoyed an encouraging week in Vegas, and though he’ll likely need to prove himself in Maine, he could factor into the plan to replace Kristaps Porzingis if he impresses in camp.

Porzingis’ recovery from offseason leg surgery, which is expected to sideline him for at least the first month of the season, could free up playing time for both Boston rookies. Mazzulla will need to lean more on his bench while his starting center heals, especially with 39-year-old top backup Horford unlikely to play major minutes each night.

A third Celtics rookie, Tristan Enaruna, signed an Exhibit 10 contract with the team and will vie for a spot in training camp. Undrafted out of Cleveland State, the 6-foot-8 forward averaged 19.6 points and 6.5 rebounds per game last season. Enaruna didn’t see much action for Boston’s Summer League team, playing a team-low 14.7 minutes per game across three appearances.