The main event of UFC 155 featured the heavyweight title fight between Junior Dos Santos and Cain Velasquez.. Cain came out hyper aggressive. He pressured Dos Santos and forced the issue with a takedown, but JDS got right back up. Dos Santos landed a good right hand as Cain came forward. A left hand landed again as Cain moved inside. Velasquez just dove for takedowns, but JDS made him pay the price. Cain dropped Dos Santos with a left and jumped on his back throwing punches. The round ended with Cain battering JDS with punches from back side control.
Cain opened up the second with a quick takedown. Everything the champ tried, Velaquez countered with apparent ease. Two minutes left in the second and Cain got another trip. Cain grabbed for an armbar but couldn't keep control. Dos Santos was gassed and Cain never stopped working. Complete dominance in the second round by the challenger.
JDS opened the 3rd round trying to maintain distance, but Cain still got a takedown in the first minute. Dos Santos performed better, but Cain still never let off him. Constantly landed shots from the clinch. Cain went for a trip going into the last minute but Junior defended with a whizzer. Big uppercut by junior but Cain looked unfazed.
Junior looked better opening the fourth round than in any of the previous. He gave up a takedown but jumped right back up. Cain tried to work the clinch. Big punches from Cain hurt Junior. This became an official war of attrition in the fourth round. Despite taking heavy body shots, Cain was relentless. His pace was too much for JDS. The final round was much like the fourth. Junior did his best to maintain distance bu constantly found himself defending Cain's clinch. Halfway through the 5th, Cain got a takedown . Junior got back up but spent the rest of the round defending.
Cain Velasquez won the Heavyweight championship with a unanimous decision (50-45, 50-43, 50-44) over Junior Dos Santos