Redshirt freshman Nate Baker will compete at 165 pounds for the top-ranked University of Minnesota wrestling team in postseason tournaments, the Golden Gopher coaching staff announced today. Baker, a native of Lakefield, Minn., takes the starting spot at 165 pounds as junior John Hardy is battling several injuries and has been deemed too big for the weight class by the coaches. Hardy, a junior from Princeton, Ind., was originally scheduled to face Baker in a wrestle-off Monday and Tuesday.    Baker will represent Minnesota at 165 pounds at the upcoming 2002 Big Ten Championships on March 9-10 in Champaign, Ill. The top seven finishers at the conference tournament and two wildcards qualify for the 2002 NCAA Championships, held March 21-23 in Albany, N.Y.    This season, Baker has put together a 25-11 overall mark (4-5 duals), placing second to Hardy at the Kaufman-Brand and Northern Opens. He took third at the UNI Open, and fifth at the Bison Open and Midlands. This past weekend, Baker stunned seventh-ranked John Clark of Ohio State, pinning the Buckeye in 6:07. A three-time Minnesota state champ at Jackson County Central High School, Baker posted a 21-3 overall record wrestling unattached at 157 and 165 pounds during his redshirt year in 2000-01.