Barnett (34-7) soundly defeated Nelson via unanimous decision on Saturday, landing 212 strikes to Nelson's 101. The five-round bout headlined UFC Fight Night at Saitama Super Arena.
It was a homecoming of sorts for Barnett, who has fought 17 of his professional fights in Japan. He holds a 13-4 overall record in the country but hadn't fought there since March 2010.
Although he was unable to record a finish, Barnett controlled the vast majority of the 25-minute fight. All three judges scored the main event for Barnett: 50-45, 48-47 and 48-47.
"The clinch work wasn't good enough, nothing I did in here was good enough tonight, but it's a good starting point," Barnett said. "We wanted to give you a finish. Roy Nelson is a champ. It's not about belts, it's about the way people fight. Roy Nelson fights like he means it. He's a f---ing warrior. He's the kind of people we need in the UFC. That's what people want to see.
"That's why I wanted to fight Roy. I gave Roy everything I had. He took it and came back. Roy is the man."
Nelson (20-12) put together a three-fight win streak in 2012 and 2013 but has gone 1-5 in six fights since. Known for his overhand right, Nelson switched it up a little on Saturday, surprising Barnett in the first round with a pair of takedowns. He caught him off-guard again in the second round with a clean head kick out of nowhere.
The high pace of Barnett, however, eventually wore on Nelson. He appeared absolutely exhausted in the third round but somehow managed to continue to go for single-leg takedowns and stand upright against punishment along the fence. Most of Barnett's offense came in close. He terrorized Nelson's midsection with knees to the body and caused swelling and bruising on the left side of his face with right elbows.
When he wasn't against the fence attempting to defend himself, Nelson was usually working on a bodylock takedown with mixed success. According to cageside stats, he converted 4 of 9 total takedown attempts, although he rarely was able to land much from top position. Late in the third round, he picked Barnett clean off of the mat and looked for a much-needed slam, but the lanky Barnett regained his balance and broke away moments later.
In the final seconds of the fight, Nelson became energized and landed several thunderous right hands that grazed off their targets. Barnett took a telling look up at the clock but made it to the final bell with no issue.
It's Barnett's first win since he stopped former UFC champion Frank Mir in the first round in August 2013. A former UFC titleholder in 2002, Barnett took a 21-month absence from the cage following a knockout loss to Travis Browne in December 2013. The 39-year-old Nelson went the five-round distance for the first time in his 11-year career.
Hall scores highlight-reel KO
Hall (12-5) allowed Mousasi to take him down in the opening minute and found himself fighting a rear-naked choke late in the first round. The former TUF standout made it to the second round, however, where he uncorked a jumping, spinning back kick that wobbled Mousasi. Hall followed the shot with a flying knee to the chin that Mousasi never recovered from. The official stoppage occurred 25 seconds into the frame.
It's easily the biggest win of Hall's career. Coming into the bout, Mousasi (37-6-2) was the No. 8-ranked middleweight in the world, according to ESPN.com. Hall improves to 5-3 in the UFC with the win.
"I know the world still thinks of me as a nice guy, but let me tell you: The best way to get the mean s--- out of me is to put me against the wall," Hall said. "My karate background is all about timing. I knew he was going to try and shoot in. If I spin, normally people will duck or flinch. When I watched him fight, the only thing I would see is he would flinch when I threw something.
"I knew I lost the first round. I had to time it and capitalize, and that's when I did my favorite kick. I followed with a flying knee. I mean, it's pretty simple."
Mousasi's confidence had to be riding high following a dominant first round. He caught an early leg kick attempt by Hall and used it to plant him on his butt. Mousasi immediately moved into side control and landed several hard punches from the top.
Hall never panicked fighting off his back and even attacked Mousasi with a leglock, although he didn't look completely comfortable doing so. Mousasi moved into full mount midway through the round, and Hall eventually opted to give him the back. The first round ended with Hall in a Mousasi body triangle, fending off chokes.
Things changed in an instant with the spinning back kick. Hall became the first fighter to ever knock Mousasi out. It's the eighth knockout of his career.
Horiguchi cruises past Camus
The 24-year-old Horiguchi (16-2) confounded Camus with his usual stick-and-move style, racking up offense while taking little damage. Unanimous judges' scores rendered a perfect shutout for Horiguchi, 30-27.
Camus (14-7) refused to give up despite losing virtually every second of the 125-pound fight. He briefly appeared to pinpoint Horiguchi's rhythm near the end of the first round, but it proved to be fleeting as Horiguchi tagged him with an early combination at the start of the next frame. Overall, Horiguchi outlanded Camus in total strikes 108 to 55.
Fighting out of Roufusport in Milwaukee, Camus committed to striking with Horiguchi for the most part, although he went for takedowns when the opportunity presented itself. He attempted to wrestle the Japanese flyweight down after Horiguchi missed on a spinning back kick but was eventually forced to give it up. He tried to impose a more physical style at times but couldn't track the elusive Horiguchi down.
Horiguchi's best moments came near the end of each round. He finished the second round with a beautiful straight left at the end of a combination and had Camus hurting late in the fight with a blitz in the center of the cage. He opened a cut under Camus' right eye with a punch in the second round and nearly took Camus' back in the ensuing scramble.
It was Horiguchi's first appearance since a fifth-round submission loss to Demetrious Johnson in a title fight in April. Other than that lopsided loss, Horiguchi has been dominant thus far in the UFC. Camus suffers his second consecutive defeat. He dropped a unanimous decision to Henry Cejudo at UFC 188 in June.
Mizugaki takes decision from Roop
Mizugaki (21-9-2) landed a handful of clean right hands and outworked Roop in the clinch, where the majority of action took place. All three judges scored the bout for Mizugaki, 29-28.
The general lack of action did little to dampen Mizugaki's spirits afterwards. The Japanese fighter broke down into tears after the win, which was his first since May 2014.
"When I lost against Dominick Cruz [last September], I thought I couldn't continue this sport," Mizugaki said through a translator. "But I love MMA. I couldn't give up. I tried hard and I got this decision. I'm so happy right now."
Roop (15-12-1) landed more total strikes in the fight, according to Fightmetric, but there was no doubt Mizugaki put together the more significant offense. He continually landed the harder shots in close and spun Roop around a bit with an overhand right in the second round. Roop, who fell to 1-3 in his past four bouts, continued to come forward as the fight progressed, but a small, late rally wasn't enough to swing the decision in his favor.
Mizugaki moves to 9-4 overall in the UFC. He put together a five-fight win streak between 2012 and 2014 before suffering back-to-back losses.
Brandao makes quick work of Kikuno
Brandao (21-10) dropped Kikuno right out of the gates with an overhand right. The Japanese featherweight hopped back to his feet but never fully recovered, and Brandao continued his assault with the right hand until the fight was called via TKO.
It's the 12th knockout of Brandao's career and his fifth first-round finish inside the Octagon. His overall record in the UFC improves to 6-3.
"My strategy was to keep the pressure," Brandao said. "He has a good front kick. I had to keep inside, inside, inside. He's dangerous."
Making his fifth appearance in the UFC, Kikuno (22-8-2) never had a chance to get going. He bounded out of his corner with his hands low, as is his typical style. He was in trouble so quick, however, cageside stats credited him with one thrown punch in the fight. After popping back up from the initial knockdown, Kikuno attempted to clinch with Brandao but ate several more right hands to the temple.
Eventually, Brandao swung him around out of the clinch and onto the floor. He fell forward facing the fence, where Brandao landed a right hand from his back that prompted referee Steve Perceval to stop the fight.
Japanese featherweights fight to a split draw
The UFC's new reality series, "Road to UFC: Japan," came to an unfortunate, rather awkward conclusion: a split draw.
Japanese featherweights Teruto Ishihara (7-2-2) and Mizuto Hirota (17-7-2) fought to a split draw in a hard-fought series finale. Scores read 29-28 for Hirota, 29-28 for Ishihara and 29-29. ESPN.com had it for Ishihara, 29-28.
The result left the two fighters speechless. Neither one appeared to know what to say at the conclusion. Referee Greg Kleynjans was also bewildered by the result and looked back at UFC announcer Bruce Buffer in confusion.
As anti-climatic as the result was, it might have been appropriate. Ishihara dominated much of the 145-pound contest, knocking Hirota down three separate times with the left hand, but he gassed badly near the end of the second round. Despite being the older man by 10 years, Hirota pushed the pace late and took advantage of Ishihara's fading gas tank in the third.
In addition to the split draw finish, the bout got off to an awkward start as Ishihara motioned to touch gloves with Hirota but threw a left kick to the body as they came together. Hirota laughed it off.
Ishihara was crisp in the opening round, targeting Hirota's lead leg with kicks, and he consistently pounded him with the counter left. The first knockdown came in the final seconds of the first round.
The pace slowly started to take a toll on the 24-year-old Ishihara, however, and he was hurt several times in the final round by right hands. Immediate cageside stats showed Hirota out-landing Ishihara in total strikes, 100 to 89.