text: After defeating former King of the Cage Super Heavyweight Champion, Dan Bobish by knockout, Rothwell was soon invited to compete in the International Fight League to fight for the Quad City Silverbacks, coached by the legendary Pat Miletich. Like several other fighters in the promotion, Rothwell was competing for the coach who he trained regularly.
  International Fight League
  On April 29, 2006, Rothwell made his IFL debut against future UFC veteran, the Polish-Canadian fighter, Krzysztof Soszynski. In the first round, Soszynski surprisingly decided to exchange strikes with Rothwell, and landed a left uppercut and held his own until he was knocked down by a short left hook from Rothwell, who then slammed Soszynski to the canvas. After working from side control and then standing again, Rothwell landed a series of punches at the end of the round, that knocked down Soszynski, and then followed this up with more punches to his downed opponent. Despite the round ending, referee Dan Miragliotta called a stop to the contest, granting Rothwell the win via TKO.
  After racking up four consecutive IFL wins, he fought future The Ultimate Fighter: Heavyweights winner and IFL Heavyweight Champion Roy Nelson, winning via split decision.
  His next fight was a rematch from almost five years earlier against veteran Travis Fulton, owner of 195 career victories. Three minutes into the second round, Rothwell secured a kimura, causing Fulton to submit.
  Rothwell then met Krzysztof Soszynski in a rematch of his IFL debut. Rothwell once again won via TKO, only 13 seconds into the bout.