Look for Anna Kournikova on NBC's "The Biggest Loser" next season.  No, Anna hasn't Blimped Out.  "New York Magazine" reports that the tennis star has signed on to fill trainer Jillian Michaels' shoes.  Anna will do her part to get contestants into shape on the hit weight loss series.  "Biggest Loser" executive producer Todd Lubin says casting Kournikova is part of a "reboot" of the series.   Lubin says next season won't be solely about numbers on the scale, but on the well-being of the contestants.  As to Anna's qualifications, Lubin says her meager upbringing in Russia is a testament to her drive.