However, for the 2012–13 season, due to the 2012–13 NHL lockout, Schwartz spent time with the Blues' American Hockey League (AHL) affiliate, the Peoria Rivermen.

[1] Schwartz helped Colorado College to an NCAA Tournament appearance, where the team was seeded in the West regional held at the Scottrade Center, in St.

[4] During his sophomore season at Colorado College, Schwartz recorded 15 goals and 26 assists for 41 points in only 30 games, missing six due to the World Junior Tournament.

[12] On March 12, 2012, Schwartz decided to forgo his final two years of NCAA eligibility and signed a three-year, entry-level contract with the St. Louis Blues, which added him to their NHL roster.

[13] After travelling and practicing with the team for a week, he was given his first opportunity for NHL play after winger Andy McDonald received a shoulder injury.

[14] Schwartz made his NHL debut on March 17, 2012, in Tampa Bay, skating on the second line with Jamie Langenbrunner and Patrik Berglund.

[16] Due to the 2012–13 NHL lockout, Schwartz was one of 25 to be sent down to the Blues' American Hockey League (AHL) affiliate, the Peoria Rivermen, to play the 2012–13 season.

[19] On September 27, 2014, Schwartz agreed to a two-year, $4.7 million contract extension with the Blues after an off-season surrounded with uncertainty about whether he would rejoin the club.

The change was made as a tribute to his late sister, who wore the number playing hockey at Yale before being diagnosed with leukemia.

[26] Schwartz got injured again, this time to his elbow, during the Blues' training camp on September 29, 2016, prior to the start of the next season.

[32] In November, after the beginning of the 2020–21 season, Schwartz's father, Rick, suffered a fatal heart attack at age 59.

[36][37] In a four-game first round playoff series against the Colorado Avalanche, Schwartz failed to score a single point.

[37] Following the 2020–21 season, his tenth with the Blues and having concluded his contract, Schwartz embarked upon free agency for the first time in his career.

On July 28, 2021, Schwartz was signed by the Seattle Kraken, an expansion team, agreeing to a five-year, $27.5 million contract.

[48] Playing Russia in the semifinal, Schwartz recorded a goal and five shots to be named Canada's player of the game in a 6–5 losing effort.

[49] He finished the tournament with two goals and three assists for five points over six games, as Canada won the bronze medal over Finland.