Spencer was a 24-year-old senior when he came out, after stops at Loyola (MD), Rutgers and UConn. His last college season was 2023-24 at UConn: 14.3 points, 4.8 rebounds and 3.6 assists in 32.8 minutes over 40 games, on 48.4% from the field, 44.0% from three and 91.1% from the line. Six boards covered him and placed him between 38th and 55th, around where Detroit took him.

Draft rights went to Memphis in July 2024 and he signed a two-way deal. His rookie year was mostly G League work (23.5 points in 8 games for the Hustle) and 25 NBA games at 10.1 minutes. The shooting held up, though: 36.5% from three in the NBA and 49.3% in the G League.

In 2025-26 he signed a multi-year contract and played 72 games with 20 starts, averaging 11.1 points and 5.6 assists on 44.9% from three and 94.0% from the line. Memphis went 25-57.

Detroit selected Spencer with the 53rd pick on Jun. 27, 2024, and RealGM lists his draft rights going to Memphis on Jul. 6, 2024, in a deal for Ulrich Chomche, another player from the 2024 class, and a conditional 2030 second-round pick. He signed a two-way contract with the Grizzlies on Jul. 8, 2024, and made his NBA debut on Nov. 20, 2024.

On Jan. 11, 2025, RealGM reported that he had fractured his left thumb in practice with the Hustle and would be re-evaluated in three weeks. On Jun. 30, 2025 he agreed to a two-year, $4.5 million fully guaranteed deal with Memphis, and on Jul. 14, 2025 that was reported as restructured into a four-year, $10.5 million contract with three seasons guaranteed. RealGM lists his free-agent timeline as team option in 2028 and unrestricted free agency in 2029.