Tuivailala was drafted by the St. Louis Cardinals in the third round of the 2010 Major League Baseball Draft. He made his professional debut for the Gulf Coast Cardinals. Tuivailala played in the outfield, shortstop and third base during his first two seasons in the Cardinals organization. After hitting only.178/.335/.256 in 42 games in 2010 and.253/.331/.329 in 44 games in 2011, he was converted into a relief pitcher before the 2012 season. Tuivailala made his pitching debut for the Johnson City Cardinals in 2012. He appeared in 11 games and had a 4.15 earned run average in 13 innings with 23 strikeouts, but issued 13 walks. The next season, he played for the Peoria Chiefs where he was 0-3 with a 5.35 ERA 28 relief appearances. Tuivailala started the 2014 season with the Palm Beach Cardinals. In July, he was promoted to the Springfield Cardinals, and in August he was promoted to the Memphis Redbirds. In 48 relief appearances between the three teams he was 2-2 with a 3.15 ERA and 1.25 WHIP. He was promoted to the major leagues on September 8. He made his MLB debut on September 9, and played in two games his rookie season. Tuivailala began 2015 back with Memphis. The Cardinals recalled Tuivailala to the major leagues on May 15. On July 1, Tuivailala was named a PCL All-Star for 2015, his first recognition as an All-Star in his minor league career. In 29 relief appearances and IP, he was 3–0 with a 1.95 ERA and 23 strikeouts. He also co-led the PCL in games finished and tied for third-most with 11 saves, converting all 11 opportunities. PCL managers and coaches rated Tuivailala the league's best reliever for 2015. He pitched in 12 games for the Cardinals in 2016, going 0-0 with a 6.00 ERA, as in 9 innings he gave up 12 hits, walked 6, and struck out 7. He was optioned to Triple-A Memphis to start the 2017 season. He spent 2017 between Memphis and St. Louis; with the Cardinals, he pitched to a 3-3 record, a 2.55 ERA, and 34 strikeouts in 42.1 innings pitched. Tuivailala made the Cardinals' 2018 Opening Day roster.
Seattle Mariners
On July 27, 2018, Tuivailala was traded to the Seattle Mariners in exchange for Seth Elledge. Tuivailala pitched to a 1.69 ERA in five games with the Mariners in 2018. In 2019, he worked to a 2.35 ERA over 23 games with the team. Tuivailala was placed on release waivers by the Mariners organization on March 20, 2020.
