[3] Tkachuk's sons Brady and Matthew would practice roller hockey in Frederic's childhood basement, sometimes joined by Logan Brown, Clayton Keller, and Luke Kunin.

[5] He spent two years in the development program, scoring seven goals and 12 assists for a total of 19 points in 58 United States Hockey League games.

In an effort to remedy this, coach Tony Granato dropped Frederic from the first to the third offensive line, where he centered Matthew Freytag and Sean Dhooghe.

[1] The offseason departure of Riley Nash to the Columbus Blue Jackets left the Bruins' third-line center position open for the 2018–19 season,[21] and Frederic entered training camp in contention with Jack Studnicka and Jakob Forsbacka Karlsson for the role.

[24] He made his NHL debut that night, skating alongside his childhood hero Backes, and received a five-minute major penalty for fighting with Winnipeg Jets forward Brandon Tanev.

[25] After 11 scoreless games for Boston, Frederic was sent back down to Providence on February 22, shortly before the trading deadline, in order to clear salary cap space for new acquisition Charlie Coyle.

[27] Although he began the 2019–20 season in Providence, injuries soon decimated the Bruins' offensive core, and Frederic was called up to Boston on November 14 to replace an injured Zach Senyshyn.

[28] His call-up was short-lived, as Frederic, Paul Carey, and Urho Vaakanainen were all sent down to Providence on November 18 to make room for Jake DeBrusk, Patrice Bergeron, and Brett Ritchie, all of whom were returning from their respective injuries.

[33] Frederic opened the 2020–21 season as a member of the Bruins' taxi squad, ready to fill in for either Craig Smith or Brad Marchand as needed.

[34] After cementing his place on the Bruins lineup by way of fighting with P. K. Subban of the New Jersey Devils early in the season, Frederic finally picked up his first NHL point on January 23, an assist on Coyle's goal in a 3–1 defeat of the Philadelphia Flyers.

[40] He began the 2021–22 season on an inexperienced fourth line with Tomáš Nosek and Karson Kuhlman,[41] where he was expected to maintain possession of the puck against opposing defense.

[47] In the second half of the season, Frederic took a less physical approach to avoid taking penalties, and he found chemistry on a line with center Charlie Coyle.

[48] Playing in 60 regular-season games as a bottom-six center and left wing, Frederic recorded eight goals and 18 points, and outgoing head coach Bruce Cassidy criticized his discipline and offensive initiative.

[52] After a poor preseason in which Frederic believed he was too concerned with making mistakes, incoming coach Jim Montgomery told him to "hunt and hit".

[55] By the end of December, the Bruins coaching staff used Frederic in all three offensive roles depending on roster injuries, but Montgomery viewed him as most creative on the right wing.

[63] On January 6, Frederic, filling in for an injured James van Riemsdyk, scored the first power play goal of his professional career against the Tampa Bay Lightning.

[5][67] The following year, Frederic helped the United States to a bronze medal with four goals and three assists in the 2016 IIHF World U18 Championships,[68] including a hat-trick in the team's 12–1 opening-round rout of Latvia.

[74] Cassidy and teammate Brad Marchand, himself a notorious pest, have also praised Frederic's ability to draw penalties from his opponents by agitating them into a fight or another infraction.