Indoor

• Started the season with a second-place finish in the 3000m at the Cougar Indoor Invitational (8:18.70)
• Set a personal record in the 3000m with a time of 8:02.19 at the Columbia Challenge (13th place)
• Finished 10th overall in the 5000m at the Iowa State Classic (14:01.19)
• Took sixth in the 5000m (14:01.96) and 10th in the 3000m (8:02.75) at the MPSF Indoor Championships

Outdoor

• Received honorable mention All-America honors after finishing 22nd overall in the 10,000m at the NCAA Outdoor Championships (31:37.34)
• Earned USTFCCCA All-Academic honors
• Took 11th place in the 10,000m (29:16.78) at the NCAA West Preliminary Round to advance to the NCAA Outdoor Championships
• Ran a career-best 28:57.83 in the 10,000m to finish 14th overall at the Stanford Invitational
• Clocked a personal record in the 5000m at the Mt. SAC Relays with a time of 13:52.12 (21st place)
• Earned a personal-best 4:17.15 to take second place in the mile at the BYU Last Chance Meet

Indoor

• Named first-team All-American after taking seventh place (7:56.72) in the 3000m at the NCAA Indoor Championships
• Named second-team All-American after finishing in 10th place (13:51.45) in the 5000m at the NCAA Indoor Championships
• Earned the third-fastest time in the indoor 5000m in BYU history with a time of 13:39.27 at the Iowa State Classic
• Ran the fifth-fastest indoor 3000m in school history with a time of 7:50.90 to take second place at the MPSF Championships
• Competed in four meets during the 2019 indoor season

Outdoor

• Named first-team All-American in both the 10,000m and 5000m at the NCAA Outdoor Championships after taking 4th (29:29.93) and 7th (14:09.20), respectively
• Earned USTFCCCA All-Academic honors
• Took fifth in the 10,000m (29:00.50) and ninth in the 5000m (13:48.69) at the NCAA West Preliminary Rounds to advance to Nationals
• Recorded the sixth-fastest 10,000m in BYU history with a time of 28:18.18 at the Stanford Invitational
• Ran the second-fastest outdoor 5000m in school history with a time of 13:29.73 at the Payton Jordan Invitational
• Earned a personal best with a time of 3:45.39 in the 1500m at the Bryan Clay Invitational
• Competed in five meets during the 2019 outdoor season

Indoor (2021)

• Set a new BYU men’s 5000m record with a time of 13:28.00 to finish first at the UW Invite. 
• Finished first in the men’s 3000m with a time of 7:58.03 at the BYU Cougar Indoor I.

Outdoor (2021)

• Finished as national runner-up in the men’s 10,000m at the NCAA Outdoor Championships with a time of 27:42.46 to garner All-America First Team honors. 
• Mantz’s 10,000m time at the NCAA Outdoor Championships ranks second all-time at BYU
• Led the NCAA with a personal-best men’s 10,000m time of 27:41.16 set at the American Track League: The Track Meet. 
• Became the first from BYU to receive Mountain Region Men’s Track Athlete of the Year since Miles Batty in 2011.
• Recorded the fourth-best men’s 1500m time in school history with a personal-best 3:37.96 at the Fresno State West Coast Relays.
• Broke the school record in the men’s 5000m with a personal-best time of 13:24.78 to finish second at the Hayward Premiere. 

Overall

• Received USTFCCCA All-Academic honors 
• Finished eighth in men’s 5000m final at U.S. Olympic Trials with a time of 13:32.69
• Finished fifth in men’s 10,000m final at U.S. Olympic Trials with a time of 27:59.37.
• Met Olympic qualifying time in men’s 5000m at 13:24.78 
• Met Olympic qualifying time in men’s 10,000m at 27:41.16 
• Named USTFCCCA Mountain Region Men’s Track Athlete of the Year