Ngata went to the locker room for further examination. His return is regarded as doubtful by the AFC champions.
The Ravens have allowed 17 unanswered points, and their 28-6 halftime lead is now down to 28-23.
Ngata had two tackles and one quarterback hit before getting hurt.
Meanwhile, rookie running back Bernard Pierce headed to the locker room after being shaken up.
Pierce was favoring his knee, limping noticeably as he was helped by trainers.
The third-round draft pick from Temple has been bothered by a bone bruise in his right knee throughout the playoffs.
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