Mizell joined the D.C. United first team staff as a goalkeeper coach under Head Coach Troy Lesesne. Mizell reunites with Lesesne after playing under him at both the Charlotte Independence and New Mexico United in the USL Championship.
Mizell spent three seasons with New York City FC where he was an Eastern Conference and MLS Cup champion in 2021 and won the 2022 Campeones Cup. He joined New York City FC on March 4, 2021 from New Mexico United after spending two seasons with the USL Championship side. Mizell is one of the original six players signed in New Mexico United club history in 2018 under former Head Coach, Troy Lesesne. He helped New Mexico United reach the quarterfinals of the 2019 Lamar Hunt U.S. Open Cup, defeating both the Colorado Rapids and FC Dallas. He also helped the club to their first playoff win in club history in 2020 before signing for New York City FC the following season. Mizell appeared in 58 matches for New Mexico United with 11 clean sheets across two seasons.
Mizell started his professional career in 2013 when he signed for the Atlanta Silverbacks of the North American Soccer League. He spent one season with Atlanta before signing with the Tampa Bay Rowdies in 2014. Mizell would appear in four matches before spending the 2015 season in the Icelandic first division with Fram Reykjavík. In one season, Mizell appeared in 19 matches, registering three clean sheets for the Icelandic side. The goalkeeper subsequently signed for Charlotte Independence on Jan. 1, 2016, where he first worked under Head Coach Troy Lesesne. In two seasons, Mizell appeared in 44 matches for Charlotte, recording eight clean sheets and was nominated for the USL Championship Goalkeeper of the Year in 2017. Mizell then spent the 2018 season with the Tampa Bay Rowdies where he appeared in 16 matches, recording four clean sheets before signing with New Mexico United. Mizell has over 10 years of goalkeeper experience in both the USL Championship and Major League Soccer.
Mizell played for Clemson University in Division I of the National Collegiate Athletic Association (NCAA) from 2010-2012. The goalkeeper was a three-year starter for the Tigers, winning numerous All-American and All-ACC awards. Mizell was named an NCAA All-American and team Most Valuable Player as a freshman in 2010. He made 51 appearances for Clemson University over three seasons before signing professionally for the Atlanta Silverbacks of the NASL in 2013.