After four years at the University of Oregon, Pritchard was selected with the 26th overall pick of the 2020 NBA Draft by the Boston Celtics. Initial expectations were low for the rookie guard, who joined a talented Celtics' depth chart. But Kemba Walker's early season knee issues made minutes available for Pritchard, and FastPP made the most of his opportunity. The Oregon product made his NBA debut on opening night, Dec. 23, and delivered three points, one rebound and one steal during a home win over the Bucks. The rookie appeared in Boston's first 14 games and averaged a surprising 7.7 points, 2.6 assists, 2.4 rebounds, 0.9 steals and 1.2 threes over 20.9 minutes per contest, while shooting an impressive 42.5 percent from behind the arc. On Jan. 4, FastPP posted 23 points and eight assists during a win at Toronto. Pritchard quickly passed veteran Jeff Teague on the depth chart, but suffered a knee injury on Jan. 22 that forced the rookie to miss seven games. Pritchard then appeared in all of Boston's remaining 52 games and five playoff games. On Apr. 27, the rookie scored a career-high 28 points, plus dealt four dimes, in a home loss to the Thunder. For the season, the rookie shot 41.1 percent on three-point attempts, which ranked second among all rookies with 65 or more attempts. In Game 4 of Boston's playoff series against Brooklyn, Pritchard posted 12 points, three assists and two rebounds over 24 minutes of run.