Former NBC News president Andrew Lack’s return to 30 Rock — he is currently in talks about a “top job” in the news division — would catalyze a major shakeup among the executive leadership and would likely signal Brian Williams’ return to the network, current and former high-level NBC News staff told the On Media blog on Monday. Lack, who served as NBC News president from 1993 to 2001, is a close friend and adviser to Williams and the man responsible for making him anchor of the NBC Nightly News ten years ago. High-level sources who spoke to On Media on Tuesday said that Lack’s return to NBC News should be taken as a near-guarantee that NBC would move to reinstate Williams as anchor of the Nightly News.