Lincoln, Neb.--Nebraska wrestling head coach Mark Manning announced Wednesday that he has received three National Letters-of-Intent for the 2002-03 season.    Highlighting the class is Matt Keller of Bradley High School in Cleveland, Tenn., who is currently ranked fifth in the nation at 130 pounds by InterMat.  A three-time state champion, Keller finished sixth last summer at Junior Nationals.  Manning said Keller will likely wrestle at 141 pounds for the Huskers.    Chad Sportelli comes from a high school familiar to the NU program.  A native of Easton, Pa., Sportelli attends Easton High School, the alma mater of current Husker three-time All-American Bryan Snyder.  Sportelli, who is currently ranked 11th nationally at 112 pounds, finished third at the state meet as a junior and fourth as a sophomore.  He is slated to wrestle at 125 pounds at NU.    Mannning's third recruit is Marc Harwood of Larefield, Minn.  Harwood has won two state titles at Jackson County High School and took fourth as a freshman.  Currently ranked 18th at 140 pounds by InterMat, Harwood is expected to wrestle at 157 pound in college.    "We're really excited to have all three as part of the Nebraska wrestling family," Manning said.  "All three will fit in well with the team and believe in the same goals and aspirations of the program."    Nebraska opens its dual schedule this Saturday at the Bob Devaney Sports Center Track with a double dual against Augustana (S.D.) and Rider.  NU will take on Augustana at 2 p.m. and Rider starting at 7 p.m.