Flaherty will make his big-league debut against the Giants on Friday, MLB.com's Jenifer Langosch reports.
With the departure of Mike Leake via a trade to Seattle on Wednesday, Flaherty will take his place and start against the Giants on Friday. During 15 outings with Triple-A Memphis this season, Flaherty has posted a 2.74 ERA and 1.14 WHIP with a 85:24 K:BB in 85.1 innings. The right-hander is a top-five prospect in the Cardinals' system, and may continue to earn starts throughout the rest of the 2017 season, especially if Adam Wainwright (elbow) cannot seem to regain full health. Over Flaherty's five August appearances, the 21-year-old has allowed just seven earned runs in 31 innings, and compiled a 4-1 record with 29 strikeouts.