Ryan Clark was penalized 15 yards for this third-quarter hit on Wes Welker, which put the Pats' leading receiver out of action for the rest of the game.

Journal photo / Glenn Osmundson

FOXBORO -- Both Wes Welker and Pierre Woods had to leave Sunday's game in the second half with head injuries.

Woods tackled Steelers tight end Heath Miller head-up at the tail end of a 19-yard first-down gain. He was announced as having a mouth injury.

The third-year linebacker has been starting at outside linebacker since Thomas broke his arm against Buffalo on Nov. 9; without him, New England is perilously thin at outside backer, and rookie Gary Guyton, who normally plays inside, took over for Woods after his injury.

Welker took his second hard hit in as many weeks when he was leveled by Ryan Clark on an incomplete pass over the middle. The pass from Matt Cassel was tipped by Troy Polamalu, but referee Ed Hochuli determined that an unnecessary roughness penalty was justified because Welker was defenseless; Clark said after the game he was told by officials he had left his feet unnecessarily.

"You can tell that was a hard hit. It must have been a hard hit if Wes Welker stays down, because he's a pretty tough guy," Kevin Faulk said.

Bill Belichick wouldn't comment on the hit to Welker, and his response when asked about Woods likely holds true for both players: "We will see what we have for next week. I am not sure where that is right now, but we'll see what we have going forward to next week. You hate to see anybody go out of the game."

smanza@projo.com