Flaherty (0-2) compiled four strikeouts and allowed an earned run on one hit over 2.2 innings in Tuesday's 1-0 exhibition loss to the Blue Jays.
Flaherty is slated open the season as the No. 5 starter with Adam Wainwright sidelined due to a hamstring injury. The 22-year-old right-hander offers plenty of upside, but the actual results at the big-league level have yet to catch up with his potential. Flaherty generated a 6.33 ERA over 21.2 innings with the Cardinals in 2017 and followed that up with a 4.60 ERA over 15.2 innings this spring (four home runs allowed).