At 25 years old, Xavier Tillman has this physical status:
High school career
He averaged 13.9 points, 7.6 rebounds, and 4.3 blocks per game during his freshman season at Forest Hills Central High School in Grand Rapids, Michigan, receiving Associated Press Class A All-State special mention awards. Tillman, a sophomore, averaged 15.5 points and 9.7 rebounds per game and led his team to the regional semifinals with a record of 23–1. He was named in the Associated Press Class A All-State special mention and to the Detroit Free Press Class A All-State first team.
Tillman revealed in the summer of 2015 that he was planning to transfer to Grand Rapids Christian High School in Grand Rapids, citing a lack of cultural diversity at Forest Hills Central and his own desire to "refocus" academically. His decision sparked a court fight between his parents because his father endorsed his transfer but his mother wanted him to remain at Forest Hills Central. He was allowed to transfer in August, but he was unable to participate in his first semester due to the Michigan High School Athletic Association's (MHSAA) transfer rules, with a request for his immediate eligibility being refused. Tillman's junior campaign with Grand Rapids Christian featured 16 points, 10.4 rebounds, and 2.9 assists, shooting 62 percent from the field to help his team win conference and district championships. He was named in Detroit News Class A Second-Team All-State honors. Tillman, a senior, averaged 13.9 points, 10.9 rebounds, 5.2 assists, and 4.2 blocks per game, guiding his team to a Class A state championship game appearance. He was named a finalist for the Mr. Basketball of Michigan award and has received the Associated Press Class A First-Team All-State distinction.
Tillman was a unanimous four-star recruiter and was rated as the top prospect in Michigan by recruiting website 247Sports. "They have the best competition in the country, as well as being such good guys," he said on September 30, 2016. It's close to home, and it's close."
In a 98-66 victory over North Florida, Tillman made his Michigan State debut on November 10, 2017, scoring four points and three rebounds. In a 93–71 victory over Stony Brook, he scored a career-high nine points, five rebounds, and three blocks. Tillman defeated Syracuse 5–53 in the second round of the 2018 NCAA tournament on March 18, 2018. He had a career-best 12 rebounds. He averaged 2.8 points, 2.6 rebounds, and 0.7 blocks per game in 35 games. Tillman received his team's Most Improved Player award as well as the Unsung Player award. He gained a lot of weight in the first season in an attempt to improve his conditioning. Tillman's weight decreased from 276 pounds (125 kg) at the start of his freshman year to under 250 pounds (113 kg) by his sophomore year.
In an 80–59 victory over Louisiana–Monroe, he earned his first double-double in his third game as a sophomore, with career-highs of 11 points and 13 rebounds. Tillman finished with 10 points and a career-best five blocks on January 21, 2019, the first single-game blocks by a Michigan State player since Jaren Jackson Jr. in February 2018. In a 71–60 victory over Rutgers, he had a career-high 19 points and ten rebounds on February 20, his career-best 19 points and ten rebounds. Tillman was named Big Ten Conference Player of the Year at the end of the regular season. He matched his career-high in scoring with 19 points and nine rebounds on March 31 to help his team beat first-seeded Duke, 68-67, defeating first-seeded Duke, 68–67. For the most part, Tillman protected Zion Williamson, the first overall pick in the 2019 NBA draft.
In a 94–46 victory over Charleston Southern on November 18, 2019, Tillman scored a career-high 21 points to go with 10 rebounds. In an 87-69 victory over Michigan on January 5, 2020, he had 20 points, 11 rebounds, and a career-high six blocks. In a 70–69 victory over Illinois, Tillman had 17 points and 11 rebounds and made a game-winning putback dunk with 6.6 seconds remaining on February 11. Tillman had 23 points and 15 rebounds in a 79-71 victory over Penn State on March 3. Tillman was named by the coaches and media as the second Team All-Big Ten and the Best Defensive Player of the Year at the end of the regular season, and he was named to the Second Team All-Big Ten by the coaches and media. As a junior, he averaged 13.7 points, 10.4 rebounds, 3.0 assists, and 2.1 blocks per game. Tillman announced for the 2020 NBA draft but ultimately decided to stay in the draft following the season.
Tillman was drafted by the Sacramento Kings with the 35th overall pick on November 18, 2020, and then traded to the Memphis Grizzlies.