SACRAMENTO – In a shot that no one seemed to see coming, least of all Joseph Benavivdez ,  Demetrious Johnson retained his flyweight title with a massive knockout on Saturday night in front of Benavidez’s hometown fans. With Benavidez throwing a left, Johnson drilled him with a right hand on the button. Benavidez’s legs gave out and he hit the canvas. “Mighty Mouse” dropped four more fists on the challenger before the stoppage came at the 2:08 mark of the first round. The flyweight title bout was the main event of today’s  UFC on FOX 9 event at Sleep Train Arena in Sacramento. It aired on FOX following prelims on FOX Sports 1 and MMAjunkie.