[4] His decision sparked a legal dispute between his parents, because his father supported his transfer, while his mother wanted him to remain at Forest Hills Central.

[5] In his junior campaign with Grand Rapids Christian, Tillman averaged 16 points, 10.4 rebounds, and 2.9 assists, shooting 62 percent from the field, to help his team win conference and district titles.

[7] He was named a finalist for the Mr. Basketball of Michigan award and collected Associated Press Class A First-Team All-State accolades.

"[14] Tillman made his debut for Michigan State on November 10, 2017, recording four points and three rebounds in a 98–66 win over North Florida.

[22] At the end of the regular season, Tillman was named Big Ten Conference Sixth Player of the Year.

[23] On March 31, in the Elite Eight round of the 2019 NCAA tournament, he matched his career-high in scoring with 19 points and nine rebounds to help his team defeat first-seeded Duke, 68–67.

[26] On February 11, Tillman had 17 points and 11 rebounds and made a game-winning putback dunk with 6.6 seconds left in a 70–69 victory at Illinois.

[34] During the Grizzlies' second play-in tournament game, Tillman recorded eleven points, seven rebounds and three steals in a 117–112 win over the Golden State Warriors.

As of April 20, 2023, Tillman scored a playoff-high 22 points, he also had 13 rebounds and no turnovers in a postseason 103–93 win against the Los Angeles Lakers in game 2.

His mother played four years of college basketball for Michigan, earning second-team All-Big Ten honors as a senior in 1990 and leaving as the program's all-time rebounding leader.

[43] Parker was a two-time state champion in both wrestling and rugby while attending Forest Hills Central High School and played football for Northwood University.

[47] Michigan State head coach Tom Izzo credited Tillman's improvement as a basketball player to Ayanna.