With just under a month to go before the start of training camp, the Celtics have a total of six non-roster players set to compete for spots this preseason.

Two of them are rookies making the jump from college (Anton Watson and Tristan Enaruna). Three others are G Leaguers with a combined 33 games of NBA experience (JD Davison, Drew Peterson and Ron Harper Jr.).

And then there’s Lonnie Walker IV.

Walker, who signed with Boston on Wednesday, is an established NBA veteran. Entering his seventh pro season, the 2018 first-round draft pick has appeared in 322 career games (with 88 starts) across stints with the San Antonio Spurs, Los Angeles Lakers and Brooklyn Nets. He hasn’t played a game in the lower-level G League since his rookie year and, at just 25 years old, should still be in his athletic prime.

Yet Walker joined the Celtics on what essentially is a training camp tryout. The one-year deal he reportedly signed is known as an Exhibit 10 contract, which is worth the veteran minimum, features no guaranteed money and includes a modest bonus if he is waived and then spends at least 60 days with Boston’s G League affiliate in Maine.

If Walker wants to land the Celtics’ 15th and final roster spot for this season – which currently is vacant with free agent forward Oshae Brissett unsigned – he’ll need to earn it.

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What can Boston expect from the 6-foot-4 wing? Ideally, an efficient long-range, off-the-bench shooter who fits well into head coach Joe Mazzulla’s 3-point-heavy approach. In 58 appearances for Brooklyn last season, Walker shot 38.4% from deep on 4.7 attempts per game, nearly identical marks to Payton Pritchard (38.5%; 4.7). Among Celtics players, only Jayson Tatum, Jaylen Brown and Kristaps Porzingis averaged more points per 36 minutes than Walker’s 20.1, which was a career high.

The Celtics also have seen the best of Walker over his six years in the NBA. In their 12 career meetings, the Miami product has posted a better field-goal percentage, true shooting percentage and offensive rating than he has against any other opponent. He’s made 50% of his career threes against Boston and hit 54% in four matchups against last year’s NBA championship squad.

The challenge for Walker – and the rest of Boston’s roster hopefuls – will be quickly proving he deserves minutes on a team that returns nearly its entire championship core. The only departures from the Celtics’ playoff roster were Brissett and reserve guard Svi Mykhailiuk, who ranked 12th and 13th on the team in minutes played during the 2023-24 regular season and hardly saw the floor during Boston’s run to the NBA Finals.

Enaruna and Harper also enter camp on Exhibit 10 contracts. Davison and Peterson re-signed on two-way contracts after spending most of last season in Maine. Watson, the Celtics’ second-round pick in the 2024 NBA Draft, is on a two-way deal, too. All five played on the Celtics’ Summer League team, as did first-round pick Baylor Scheierman, who signed for four years and $12.8 million to fill one of Boston’s two roster vacancies.

Brady backs Tatum

Tatum’s handling of his role reduction at the Summer Olympics earned him plaudits from Tom Brady.

Commenting on an Instagram post that shared recent comments Tatum made about his “challenging” experience in Paris, the former Patriots quarterback praised the Celtics star for his professionalism, calling him a role model for younger athletes.

“A true professional!” Brady wrote. “A true champion! And a great teammate! We should celebrate people who care more about the team success than the individual success! There are so many people involved in every organization who don’t always play a ‘starting’ role but play a huge role in the success of the team. I have more respect for Jayson Tatum now more than ever! (N)ow this is what we should be teaching our kids!”

Tatum, a first-team All-NBA selection in each of the last three seasons, logged the second-fewest minutes of any Team USA player and did not play in two of the six games (both against Serbia), sparking criticism of U.S. head coach Steve Kerr.

“Obviously, I wanted to contribute more, and I’ve never been in (this) situation,” Tatum told The Athletic’s Jared Weiss. “I started playing basketball at (age) 3 at the YMCA, and I’ve never not played, so it was different and it was challenging.”

He added: “I wasn’t moping around. I didn’t have an attitude. I wasn’t angry at the world. I stayed ready and did what was asked of me and I won a gold medal, right?”

Brady’s comments echoed Jrue Holiday’s take on the situation. Holiday was one of three Celtics players on Team USA.

“I think everybody here knows JT,” Holiday said earlier this week. “He’s the ultimate professional. He already knows what it is and what the ultimate goal is, and I don’t think he really needed any encouragement. I think it was just more so about staying ready whenever it’s his time to be called.”

Off the rim

Another Celtics Olympian, Derrick White, received a standing ovation during Thursday night’s University of Colorado football game. White, a Colorado native, played his senior season for the Buffaloes after transferring from Division-II University of Colorado Colorado Springs. He watched Deion Sanders’ squad hold off an upset bid to beat North Dakota State 31-26. … A busy week for Joe Mazzulla. The Celtics head coach spoke at West Virginia’s football season kickoff event last Saturday, addressed the Trinity College football team on Monday and visited Patriots practice on Thursday. … Ex-Celtic Glen “Big Baby” Davis had the start of his 40-month prison term delayed until Oct. 22 to allow for the completion of a documentary about his life. The 2008 NBA champion was convicted of health care fraud in 2023.