One day after the latest Nielsen ratings indicated that ABC World News with Diane Sawyer had overtaken NBC Nightly News with Brian Williams among 18-49-year-old viewers the first time in 243 weeks and was barely 200,000 viewers behind among total adults, Williams announced that he will undergo knee replacement surgery and will be leaving the newscast while he recovers. I've paid a very high price for what's been confirmed to be the single worst New Jersey High School Catholic League football career in history, he said. His absence will give the ABC newscast an unexpected opportunity to draw viewers away from NBC, which has already seen its once-dependable Today show also fall behind its ABC competition. Williams said that he will be leaving the newscast around the middle of next week and that Lester Holt will be replacing him while he recovers. He indicated that he will probably be gone several weeks.