Per the Steelers' official injury report, Watt has already been ruled out after not being able to practice on Thursday or Friday.
On Tuesday, per NFL Network's Tom Pelissero, Watt was diagnosed with a "low-grade groin strain." He suffered the injury during the first half of Pittsburgh's 26-9 win over the Minnesota Vikings in Week 2 and didn't return.
Per Ray Fittipaldo of the Pittsburgh Post-Gazette, Watt said it "wasn't serious."
When healthy, the 22-year-old has the ability to be an impact player on the Steelers defense. Although he was more known as the younger brother of Houston Texans star J.J. Watt, T.J. has shown he is more than that and has made a name for himself early in his football career.
He kicked off his Steelers tenure with two sacks and an interception in his first game before getting hurt in Week 2.
Pittsburgh has quality depth at linebacker between Bud Dupree and James Harrison to fill in if Watt is forced to miss more time, although the team doesn't want to be without one of its key players for too long.