That's why Boston has no plan to waive him before Tuesday's deadline, which would be an absurd idea considering the impact he made as a rookie in limited minutes.
When Boston signed him last July, it was a two-year deal with his contract for this season becoming fully guaranteed unless he was waived by July 10.
Not only did he become a solid contributor for Boston as a rookie, but he was also one of the team's biggest bargains when you factor in his play relative to his $815,615 rookie salary, which will increase to $1.378 million for next season.
Upon arrival in Boston, there were lots of questions surrounding the 6-foot-9 Theis and exactly what kind of impact he could make on the team.
He had proven himself to be a strong defender in Germany, in addition to having a championship pedigree having won three consecutive German League titles with Brose Bamberg (2015-2017).
It didn't take long before his impact on the floor provided a dimension to the Celtics lineup that would prove invaluable, helping Boston finish with the second-best record in the Eastern Conference.
Theis provided an above-the-rim presence on lob passes in addition to doing a good job as a pick-and-roll defender, showcasing the kind of versatility the Celtics love in all their players.
Theis was well on his way to being a player Boston would count on as a key reserve in the playoffs, only for a torn meniscus injury to end his season after just 63 games.
In his first season with Boston, Theis averaged 5.3 points and 4.3 rebounds in just 14.9 minutes while shooting 54.1 percent from the field.