Devin Carter is out for the Boston Celtics‘ season opener Tuesday in Detroit, the lone name on their first injury report, with mononucleosis, according to CLNS Noa Dalzell. But outside of Carter’s malady, the Celtics are reported to be fully healthy as they head into the 2026-2027 season.

Carter signed his two-way contract Saturday, and the mononucleosis diagnosis reported Sunday leaves him without a timetable to return, according to CBS Sports.

The diagnosis became public Sunday, Oct. 18, when Boston Globe columnist Gary Washburn reported it. That explained Carter’s disappearance from the lineup after the Oct. 8 preseason opener against Cleveland. He sat out the final three preseason games with an illness that went unspecified until the diagnosis surfaced.

Boston Celtics Rotation Players Healthy for Pistons Game

With Carter the only absence, Jayson Tatum, Paul George, Derrick White, Payton Pritchard and Mitchell Robinson are all available, Dalzell reported. Tip-off is 3 p.m. EDT at Little Caesars Arena.

Detroit finished last season as the East’s top seed, while Boston won 56 games. The Pistons re-signed center Jalen Duren, who will test Robinson and Neemias Queta, and added John Collins, Isaiah Joe and Taurean Prince. Cade Cunningham and Ausar Thompson return.

“I love this team. I love who we can become,” Celtics coach Joe Mazzulla said, as quoted by the Globe. He wants to see how Boston responds to adversity, long streaks and compressed schedules.

Boston traded Jaylen Brown to the Philadelphia 76ers for George and two first-round picks, and added Robinson and Mike Conley Jr. in free agency, according to NBC Sports Boston.

With Brown gone, Tatum enters the season as the unquestioned team leader and top option for the first time in his career.

“Obviously, JT is the guy,” George said, as quoted by the Globe.

The Celtics play 13 of their first 21 games on the road, a stretch that includes the Knicks, Rockets, 76ers, Nuggets, Warriors and Spurs.

NBC Sports Boston’s season simulation, carried out by the Strat-o-Matic sports game company, projected a 47-35 record and a fourth-place finish in the East. In the Strat-o-Matic simulation, the Celtics go on a deep playoff run, beating Philadelphia, Detroit and the defending NBA champions New York Knicks to reach the Finals, before losing in seven games to the San Antonio Spurs, Goss reported. Tatum falls short of first-team All-NBA numbers in that simulation, and George averages just under 18 points per game.

Devin Carter’s Background and Boston Celtics Arrival

Carter, 24, was born March 18, 2002, played at Providence and went 13th overall to the Sacramento Kings in the 2024 draft, according to NBA.com.

Shoulder surgery consumed much of his rookie year, and he did not debut until January 2025. Over 74 games across two seasons in Sacramento, Carter averaged 6.4 points, 2.7 rebounds and 1.9 assists in 14.8 minutes while shooting 27.4 percent from three-point range, according to Hoops Rumors.

The Kings attached a second-round pick to Carter in a June trade with Atlanta to get beneath the tax line. The Hawks waived him in September, and Boston signed him to a training camp contract, Adams reported.

Carter’s lone preseason appearance for the Celtics came Oct. 8 against Cleveland. He scored 17 points with five rebounds and three assists in 25 minutes, and Boston outscored the Cavaliers by 22 points while he played. The conversion to a two-way deal followed, a contract that pays $678,882 and allows up to 50 regular-season games, according to Adams.