Schmaltz played collegiate hockey with the University of North Dakota after playing in the United States Hockey League (USHL) with the Green Bay Gamblers, where he won the 2012 Clark and Anderson Cups. He also received First-Team honors of the USHL. In 2011, he was traded to the Gamblers from the Sioux City Musketeers, where he was named to the 2010–11 USHL All-Rookie Team and also to the USHL First All-Star Team.[2][3]
Schmaltz spent three seasons playing for the University of North Dakota in the National Collegiate Hockey Conference (NCHC). On May 28, 2015, he announced that he would forgo his final year of NCAA eligibility and signed a three-year, entry-level contract with the St. Louis Blues.[4] He made his NHL debut in a 3–0 win over the Colorado Avalanche on March 5, 2017.[5]
On December 12, 2017, Schmaltz was recalled to the Blues to replace injured captain Alex Pietrangelo.[6] Schmaltz was selected for the 2018 AHL All-Star Game but was unavailable to play.[7] He was replaced by Tucson Roadrunners' defenseman Kyle Capobianco.[7]
On September 13, 2018, Schmaltz signed a two-year contract extension with the Blues.[8]
As a free agent from the Islanders, Schmaltz went unsigned during the break. Approaching the delayed 2020–21 season, Schmaltz accepted a professional tryout invitation to attend the Arizona Coyotes training camp, joining his brother Nick, on December 28, 2020.[11] After his release by the Coyotes following training camp, Schmaltz joined the Tucson Roadrunners on a professional tryout contract.[12]
After six North American professional seasons, Schmaltz opted to sign abroad as a free agent, joining Finnish club, HIFK of the Liiga, on June 16, 2021.[13] After a year in Finland, Schmaltz signed with EHC Kloten of the Swiss NL in February 2022.[14]
Schmaltz attended the University of North Dakota and majored in Communication and Social Science. His father and two uncles, Marc and Monte, also attended college there, and lettered in football.[17]
Schmaltz designs golf apparel for his company, Butter Golf.[18]