On July 3, 2019, the Tigers selected Alexander's contract and promoted him to the major leagues as the 26th man of a doubleheader against the Chicago White Sox.

[7] In his major league debut, he pitched five innings, allowing two runs and recording four strikeouts (including the very first batter he faced).

[8] On September 16, Alexander pitched six innings of one-run baseball against the Baltimore Orioles, earning his first major league win.

He also tied the American League and Tigers' franchise record of nine consecutive strikeouts set by Doug Fister on September 27, 2012.

[13] He began the season as a long reliever and occasional "opener" (pitching the first two to three innings of a game), before being moved to an official starting role in July.

[14] On August 20, Alexander pitched a career-high seven innings and allowed only one run against the Toronto Blue Jays to record his first quality start of the season.

[16] On September 19, Alexander took a no-hitter into the seventh inning against the Baltimore Orioles before surrendering a leadoff single to Ryan Mountcastle.

He made 25 appearances, recording a 4.50 ERA with 44 strikeouts in 44.0 innings of work before he was placed on the 60-day injured list with a lat strain on July 4, 2023.

This was the 2nd longest perfect game bid in Rays history, behind the duo of Ryne Stanek and Ryan Yarbrough in 2019 and Drew Rasmussen in 2022, both 8 innings vs the Orioles.