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Johnson was aggressive early but del Rosario took him down and finished him on the ground.
Johnson shoved del Rosario early and knocked the youngster off balance. But del Rosario was quickly able to force a clinch. Johnson surprised del Rosario by forcing the take down. Johnson worked for ground and pound but didn't score much before del Rosario stood up. Johnson then quickly clinched and landed a knee to the face. DRosario opened up with lefts and jabs and forced another clinch. Del Rosario landed a knee to the body. They separated and del Rosario landed again and followed up with a take down. He quickly advanced from side control to mount. Del Rosario rared back and began to land punches from the top. Del Rosario controlled position and continued to rain down blows but wasn't doing much damage. Then he went for the arm bar and submitted Johnson with 30 seconds left in the round.
The 27 year old del Rosario came into the fight regarded as one of the best prospects in the heavyweight division. Johnson, 33, is best known for having survived a random gang shooting in 2009.