Tarnok was recalled from Triple-A Las Vegas ahead of Friday's game against the Twins.
Tarnok has been working as a starter at Triple-A, logging a 2.12 ERA, 1.24 WHIP and a 9:9 K:BB in 17 innings over his four most recent outings. The 24-year-old righty could work in tandem with a lefty like Ken Waldichuk, but it's not initially clear when the former will make his first MLB appearance of the year and whether it will be as a starter or long reliever.