Watt recorded two tackles prior to his exit, and the Steelers were leading Minnesota 20-9 in the third quarter when they announced that he wouldn't return.
After leading the Big Ten with 11.5 sacks last season, the linebacker's game quickly translated to the NFL with two sacks and an interception in his first game. Per ESPN Stats & Info, he was the first player in 30 years to accomplish this feat.
Unfortunately, the latest injury could put a damper on his development and take a key player off the field for Pittsburgh.
The Steelers have other options at outside linebacker like James Harrison and Bud Dupree, but they will hope their star rookie will be able to return to the field before too long.