The Pittsburgh Steelers are not the same team without T.J. Watt, and they saw their superstar defender go down with a knee injury Saturday.

On Sunday, J.J. Watt, T.J.'s older brother, posted on X — formerly known as Twitter — that his younger brother sustained a Grade 2 MCL sprain.

"Best case scenario for TJ," J.J. said. "Everything else looks pristine. Couple weeks of rest/recovery."

With that timeline, if the Steelers do make the postseason, then Watt will likely miss the first round. Pittsburgh either needs a loss or tie by the Jacksonville Jaguars or loss by the Buffalo Bills to get into the playoffs.

Watt was following a play when Baltimore Ravens quarterback Tyler Huntley rolled out, and jumped up to try and bat down a pass. When he landed, teammate Montravius Adams came down and hit Watt in the left knee. Watt stayed down while teammates took a knee around him with concerned looks.

Watt went to the medical tent, then walked slowly back to the locker room. He had his gloves off, which indicated his day was done. If Watt could return he surely would have, considering the Steelers were fighting for a playoff spot in Week 18.

Not long after that, Watt was ruled out.

ESPN's Adam Schefter said the initial diagnosis was a sprained MCL for Watt, and that he wanted to go back in the game but the Steelers staff wouldn't allow it. On Saturday, Watt was believed to have suffered a Grade 3 sprain, a severe sprain that could keep Watt out multiple weeks, according to NFL Media's Ian Rapoport.

Watt was having a big day. He got his 19th sack, taking over the NFL lead. That made some history and put him on the doorstep of some more history.

Then the injury happened. Watt is the Steelers' best player and perhaps the best defensive player in the NFL. The Steelers had more to worry about than just their playoff future during Saturday's game.