During the 2020 offseason, Semi Ojeleye decided to return to the Celtics for his fourth season in the Association. The wing appeared in 56 of Boston's 72 games, with 15 starts. The 15 starts were a career high, as were Ojeleye's 4.6 points, 2.6 rebounds, 0.7 assists and 1.0 made three-pointers per game. Ojeleye also played a career-best 17.0 minutes per game. On Jan. 4 in a road win over Toronto, the SMU product grabbed a career-high-tying eight rebounds to go with 12 points. On Feb. 11, Ojeleye scored a career-high 24 points, adding six rebounds and a career-best six three-pointers during a home win over the Raptors. A late March hip injury slowed down Ojeleye during the back half of the season. The forward appeared in 16 of Boston's last 28 regular-season games, though he did start six times during that span. Ojeleye made two brief appearances during Boston's five playoff games versus Brooklyn, totaling one point, one steal and one block over 12 minutes of action. Ojeleye enters the 2021 offseason as an unrestricted free agent.

Ojeleye's third NBA season again saw him serve in a valuable bench role for the Celtics. The muscular wing played in 69 out of 72 regular-season games, making six starts during the coronavirus-shortened season. The SMU product posted career highs in points per game (3.4), assists per game (0.5), three-pointers per game (0.7) and three-point shooting (37.8 percent). His 14.7 minutes per game represented a significant increase from the prior season's 10.6. On Dec. 9, "The Ox" grabbed a career-high four steals in a home win over the Cavaliers. On Mar. 4 against Cleveland, Ojeleye scored a career-best 22 points thanks to a career-high five three-pointers, adding six rebounds, two assists and one block over 30 minutes. All told, he posted double-figure scoring totals five times. Ojeleye played in all seven Orlando seeding games within the NBA bubble, twice scoring in double figures. One of his best games of the season came in the bubble, as he scored 13 points with a career-high eight rebounds against the Wizards on Aug. 13. He went on to appear in 13 of Boston's 17 postseason games. In Game Game 4 of the second-round series against Toronto, Ojeleye set a new postseason best with seven points in 11 minutes of play. All told, he averaged 1.6 points and 0.4 made three-pointers over 9.4 minutes per game during the playoffs.

A relatively healthy Celtics roster led to a decline in playing time for Ojeleye in his sophomore season of 2018-19. The return of Kyrie Irving and Gordon Hayward resulted in Ojeleye appearing in only 56 games (three starts) and averaging 10.6 minutes per contest. However, he improved in a number of metrics despite the cut in playing time. Ojeleye actually bested his rookie scoring mark with 3.3 points per game -- that's 11.3 points on a per-36-minute basis -- thanks to a much-improved 42.4 field-goal percentage. The Celtics finally unleashed him for 38:13 on the court in the final game of the regular season, Apr. 9 against Washington, and Ojeleye responded with a career-high 17 points along with four rebounds, three assists and a steal. But Ojeleye had delivered some other eye-opening performances in limited time over the course of the year. Most impressively, on Dec. 8 at Chicago, he scored 13 points in just 14:25 on the court, hitting 3-of-6 from downtown. Ojeleye found his way into the lineup for six of the Celtics' nine playoff games, and he set a new playoff best with six points in just 11:02 during Game 3 of their second-round series against the Bucks.

Ojeleye was drafted by the Celtics with the seventh pick of the second round out of Southern Methodist and went on to play a major bench role in his rookie year, appearing in 73 games (all as a reserve). Ojeleye's gritty defense meant he was often tasked with coming off the bench to slow down opponents' top scoring wings. The muscular Kansas native also banged inside versus a few power forwards. Ojeleye's ability to guard players of different positions was a strong fit with coach Brad Stevens' switching defensive scheme. On the whole, he averaged 2.7 points (including 0.5 threes) and 2.2 rebounds in 15.8 minutes per game. He cracked double-digit points twice, setting his personal best Apr. 8 against Atlanta with 13 points and six rebounds. Come playoff time, Ojeleye again played a vital defensive role. He also made the first three starts of his career in the Celtics' first-round series against Milwaukee, largely tasked with guarding Giannis Antetokounmpo.