Tiernan suffered a left ankle injury during Saturday's preseason win against the Giants, Ben Goessling of The Minnesota Star Tribune reports.
Tiernan struggled a bit in his first NFL game action after being drafted in the third round of April's NFL Draft. The Northwestern product also picked up an ankle injury, so it wasn't the preseason debut he had envisioned. Coach Kevin O'Connell didn't elaborate on the extent of Tiernan's injury, and it remains to be seen if he'll be able to play in Minnesota's next preseason contest, which is slated for next Saturday against the Ravens.