The Athletics selected Waldichuk's contract from Triple-A Las Vegas ahead of his scheduled start Thursday in Washington.
Oakland designated right-handed reliever David McKay for assignment to clear room on the 40-man roster for Waldichuk, who will be making his big-league debut Thursday. The 24-year-old lefty, whom the Athletics acquired in the Aug. 1 deal that sent Frankie Montas to the Yankees, posted a 3.53 ERA, 1.27 WHIP and 91:26 K:BB in 66.1 innings across 15 starts at Las Vegas and Triple-A Scranton/Wilkes-Barre on the season. With a strong showing over his starts with Oakland in the final five weeks of the season, Waldichuk could stake his claim to a permanent rotation spot with the Athletics heading into the 2023 campaign.