Nelson was added to the card after the event lost the interim bantamweight title fight, hoping to add some entertainment and knockout potential. Miocic, while further down in the rankings, was the only man brave enough to answer the call to fight "Big Country" on short notice.
Record: 19-7 overall, 6-3 in the UFC
How he got here: Roy Nelson made his mark outside the UFC, most notably as the inaugural IFL heavyweight champion. After defending the strap twice, the promotion folded and "Big Country" stepped in on 10 day's notice to take on former UFC heavyweight champion Andrei Arlovski under the Elite XC banner. Nelson was in control of the bout but a horrible stand-up ruined his night and allowed Arlovski to score a knockout victory.
The beer-bellied brawler would redeem himself on The Ultimate Fighter season 10, easily grappling his way to the finale where he would blast Brendan Schaub in the first round of the finals to win the show's title. He followed it up by taking out "The Skyscraper" Stefan Struve with another first round knockout.
Nelson earned a number one contender fight with Junior dos Santos at UFC 117 for his efforts but was battered for three straight rounds, showcasing an incredible ability to absorb punishment in a decision loss. He would drop another decision to fellow Las Vegas resident Frank Mir in his next bout in a listless performance.
"Big Country" bounced back with a third round technical knockout of the legendary Mirko Filipovic at UFC 137, but he was brought back down to Earth against Fabricio Werdum, enduring some serious punishment over the course of three rounds.
His roller coaster UFC career continued in his last three fights, scoring impressive first round knockouts of Dave Herman and Matt Mitrione and Cheick Kongo respectively. Now, he's in line for another opportunity to climb up the heavyweight ranks if he can get past Stipe Miocic
How he gets it done: The most important thing of all for the Las Vegas native is to explode with his right hand in the pocket. Nelson has a big overhand right which he throws with great force, but he first must close the distance whether it be simply utilizing decent footwork or using his surprising dexterity to lunge forward as a gap-closer.
Nelson is strong enough on the ground as well as physically that he should be able to avoid Miocic's wrestling if he's not being overexuberant with his attack.
The TUF 10 winner also has a tremendous chin he can rely on. The ability to absorb punishment is not always something to be proud of, but Nelson's chin is much sturdier than Miocic's so he shouldn't be afraid to eat a shot in order to dish one out.
If Nelson hurts Miocic with any of his strikes, he needs to pounce and try to put him away quickly, although time is on his side as Miocic has shown conditioning flaws in the past.
Record: 9-1 overall, 3-1 in the UFC
Key Losses: Stefan Struve (UFC on Fuel TV 5)
How he got here: Stipe Miocic is an athlete, plain and simple. He was a successful collegiate wrestler and baseball player while attending Cleveland State University. After becoming a fireman/paramedic, he was requested to help train with Dan Bobish to prepare the MMA pioneer for an upcoming fight and he never looked back once he'd gotten a taste of MMA.
The former Golden Gloves boxer started his professional career in 2010, winning by knockout in all four of his fights while competing primarily for NAAFS in Ohio. His 2011 got off to an equally impressive start, winning two more fights via strikes before getting the call to the UFC.
The Croation-American made his promotional debut at UFC 136 on the preliminary card against brawler Joey Beltran. Miocic utilized strong kicks while mixing in takedowns to earn a unanimous decision against "The Mexicutioner."
He was pitted against Philip De Fries earlier this year and after eating a few punches in the opening seconds, he knocked the English submission wiz senseless inside the first minute of the first round. He followed that up by handing former kickboxing champion Shane Del Rosario his first career defeat, smashing the Team Oyama fighter via brutal second round ground and pound.
With his impressive start, Miocic headlined his first show against Stefan Struve and after a good start, he failed to keep up the pace and was finished via second round TKO.
How he gets it done: If Miocic is going to win this fight, he needs to make proper adjustments. He loves to stand and bang, but that's not how he wins this fight.
Roy Nelson is too dangerous, too powerful and can take too much punishment and keep going forward for Miocic to risk standing and banging in the pocket while expecting to come out on top.
The key for Miocic is whether or not he can take the fight to the ground. Nelson is renowned for his striking game, but Shane Del Rosario was talented on the ground as well and Miocic pounded the hell out of him. If Miocic can secure top position, hold Nelson down and drop big strikes, he's got a chance of at least winning a decision. He has to go back to his roots though.
Who will come out on top at UFC 161? Tell us your predictions in the comments below!