The 27-year-old Lyons was 2-1 with a 2.91 ERA in four starts for Memphis with 26 strikeouts in 21 1/3 innings. He threw eight shutout innings against Rock Round his last start on April 28.
Lyons is 2-8 with a 4.62 ERA in 23 career major league appearances, including 12 starts. He worked 4 2/3 scoreless innings in relief with a career-high eight strikeouts in the first game of a doubleheader against the Cubs on Aug. 30, 2014.
Tuivailala appeared in one game with St. Louis, allowing one run in two innings Sunday against the Pirates.