[9] He worked the 1989 Memorial Cup in Saskatoon as a linesman,[13] then attended the annual National Hockey League (NHL) training camp for the best young officials in 1990.
[13] After half a season, he reverted to his former role as he felt that he could realize his dream of reaching the NHL quicker as a linesman than as a referee.
[18] In 1993, the ten trainees, including Hasenfratz, all declined offers to be replacement referees if the NHL officials went on strike.
[22] He refereed the 1998 WHL All-Star Game in Regina,[23] and received the Allen Paradice Memorial Trophy as the league's official of the year in the 1999–2000 season.
[21] In July 2000, Hasenfratz signed an officiating contract with the NHL, expecting to work mostly American Hockey League games for the 2000–01 season.
[24] Hasenfratz made his NHL debut during the October 21, 2000, game between the New York Islanders and the Washington Capitals at the MCI Center.
[25][26] His other crew members included referee Paul Stewart, and linesmen Gord Broseker and Pat Dapuzzo.
[27] Hasenfratz's first playoff assignment was game two of the 2002 Western Conference quarterfinals between the Vancouver Canucks and the Detroit Red Wings.
[33][34] Upon returning to the NHL, he changed to uniform number 2, to signify getting a second chance after two surgeries, and for having the "world's second-best job, right after playing".
[4][9] Hasenfratz worked his final game on March 16, 2014, between the Philadelphia Flyers and the Pittsburgh Penguins at the CONSOL Energy Center.
[22][d] In September 1991, he resigned as a constable with the Regina Police Service to follow a full-time career officiating ice hockey.
[17] He moved to Burnaby, British Columbia, in August 1991, and appeared as an extra in a hockey fight scene in the 1992 film Stay Tuned.