Theis with Germany in 2014
|No. 27 - Boston Celtics|
|Position||Center / Power forward|
|Born||April 4, 1992|
|Listed height||6 ft 8 in (2.03 m)|
|Listed weight||245 lb (111 kg)|
|NBA draft||2013 / Undrafted|
|Career highlights and awards|
|Stats at NBA.com|
|Stats at Basketball-Reference.com|
Born in Salzgitter, Theis went through the Braunschweig youth system. He made his debut in the German top-tier level league, the Basketball Bundesliga, during the 2010-11 season. Theis primarily gained playing time with the club's development squad, where he played alongside his older brother, Frank, from 2010 to 2012. He earned the Eurobasket.com website's All-2.Pro B Most Improved Player of the Year honors in 2011. In Braunschweig, Theis was also a teammate of fellow NBA player Dennis Schröder.
In the 2013-14 season, while with ratiopharm Ulm, Theis won the BBL Best Young Player award. Following his breakout season with Ulm, Theis signed with fellow German Bundesliga club Brose Bamberg. In the 2014 off-season, he played in the 2014 NBA Summer League for the Washington Wizards' summer league team.
In the 2014-15 season, Theis won his first German League championship with Brose Baskets. Brose beat FC Bayern Munich 3-2 in the German League Finals. In April 2015, he signed a fresh two-year deal with the Bamberg team, and he won two more German championships with Bamberg, in 2016 and 2017.
On July 20, 2017, Theis signed with the Boston Celtics. He made his NBA debut on October 18 against the Milwaukee Bucks. On March 12, 2018, Theis suffered a torn meniscus in his left knee, and missed the remainder of the 2017-18 season after Theis repaired his left knee lateral meniscus in a surgery.
On October 29, 2018, Theis was found to have a slight tear of the plantar fascia in his right foot and was scheduled to be out indefinitely, but he returned shortly after the injury on November 11 vs. the Portland Trail Blazers.
On July 17, 2019, the Boston Celtics announced that they had re-signed Theis, along with former Brose Bamberg teammate Brad Wanamaker. The contract was reported to be worth $10 million in total for the 2019-20 and 2020-21 seasons.
Two thirds through the season, on February 21, 2020, Theis had a career-high 25 points and 16 rebounds in a win against the Minnesota Timberwolves. Theis continues to complement the rest of the starters, playing in a way that "fits the other guys perfect" according to coach Brad Stevens.
Theis was a member of the junior national teams of Germany. With Germany's junior national teams, he played at the 2011 FIBA Europe Under-20 Championship, and the 2012 FIBA Europe Under-20 Championship.
On July 27, 2014, Theis made his first appearance with the senior German national basketball team in a game against Finland. With Germany's senior team, he played at the EuroBasket 2015 qualification tournament.
Note: The EuroLeague is not the only competition in which the player participated for the team during the season. He also played in domestic competition, and regional competition if applicable.