Portillo began his collegiate career for the University of Michigan during the 2020–21 season. During his freshman season, he appeared in seven games and posted a 4–1–0 record with a 1.67 GAA and .935 save percentage.[3] He made his collegiate debut for Michigan on 3 December 2020, in relief of Strauss Mann, stopping 15 of 17 shots in a 9–5 loss against Penn State.[4] He made his first career start on 15 January 2021, making 19 saves in a 4–2 victory against the Ohio State.[5]
During the 2021–22 season, his sophomore season, Portillo posted a 31–10–1 record with a 2.14 GAA and a .926 save percentage in his first full season as a starter.[6] He led the nation in saves (1,111) and ranked second in wins (31) and minutes played (2,499), fourth in win percentage (.750) and ninth in save percentage (.926).[3] He posted his first career shutout on 28 October 2021, in a 3–0 victory against Wisconsin, stopping all 28 shots he faced.[7] During the 2022 Big Ten tournament, he posted a 4–0 record with a .928 save percentage, and also recorded 90 saves on 95 shots he faced during the tournament. He was subsequently named to the Big Ten All-Tournament Team and named tournament's Most Outstanding Player.[8][9] Following the season he was named second-team All-Big Ten, a semifinalist for the Mike Richter Award and a finalist for the Big Ten Goaltender of the Year.[10][11][12]
On 9 April 2022, Portillo announced he would return to Michigan for his junior year for the 2022–23 season.[13] During his junior season, he posted a 25–11–2 record with a 3.00 GAA and a .908 save percentage and helped lead the Wolverines to their second consecutive Big Ten tournament championship and Frozen Four appearance. He finished his collegiate career with a 60–22–3 overall record, 2.49 GAA, and a .918 save percentage.[14]
Professional
Portillo was drafted in the third round, 67th overall, by the Buffalo Sabres in the 2019 NHL entry draft.[15] He announced he would not sign with the Sabres and would pursue unrestricted free agency after his college career at Michigan. On 1 March 2023, the Sabres traded his draft rights to the Los Angeles Kings in exchange for a 2023 third-round pick.[16][17]
On 10 April 2023, Portillo signed an amateur tryout contract (ATO) with the Kings' AHL affiliate, the Ontario Reign.[18] On 22 April, the Kings signed Portillo to a two-year, entry-level contract through the 2023–24 season.[19] During the 2023–24 season, in his rookie season, he appeared in 39 games with the Reign and posted a 24–11–3 record with a 2.50 GAA and .918 save percentage. His 24 wins were the most by a rookie goaltender in franchise history.[20]
On 25 August 2024, Portillo signed a three-year contract extension with the Kings through the 2026–27 season.[21][22] Portillo began the 2024–25 season with the Reign, where he appeared in six games and posted a 4–2–0 record with a 2.68 GAA and .906 save percentage. On 15 November 2024, he was recalled by the Kings on an emergency basis after placing starting goaltender Darcy Kuemper on the injured reserve.[23][24] He made his NHL debut on 29 November 2024 in a game against the Anaheim Ducks, making 28 saves in a 2–1 victory to record his first career NHL win. During the third period, Portillo's skate blade was dislodged and forced him out of the game for 1:23, David Rittich entered in relief before being replaced by Portillo following the equipment fix.[25][26]