Knack was optioned to Triple-A Oklahoma City on Sunday.
Knack made two appearances, including one start, this spring, allowing two earned runs on one hit and a walk while striking out seven batters over four innings. The right-hander produced a 2.93 ERA with 38 strikeouts over 43 frames in 10 starts with Oklahoma City last year, and if he repeats that production, he'll likely earn a shot in the majors sooner rather than later.