Tonje, drafted 53rd overall by the Jazz in 2025, began his pro career with the Salt Lake City Stars. He was traded to Boston on Feb. 5 in a deal that included Chris Boucher.
After a 10‑day NBA contract and a debut on Feb. 24, Tonje scored his first points on Feb. 27. The two‑way deal keeps him eligible for both the Celtics and their G League affiliate.