Prior to the fight which was scheduled for 10 rounds O'Brien had five wins, a draw and a loss as a professional. Nawai had 11 wins, eight of them by knockout. A former light middleweight, O'Brien, relished the underdog tag.
"Everything was against me. We had to wait 90 minutes for the fight, he was on home soil and in his backyard. I had everything to gain and nothing to lose ... I loved it."
After the fight O'Brien said he had at least three different promoters coming up to offer him fights on different shows.
"But I told them I need a break because Lisa [partner Timu] and I are getting married in August. That's my main focus for the next seven weeks and then we will see what fights are available."
"In the meantime I'm on the hunt for a nice big chocolate cake. I haven't had one all year because it takes a 21km run to work it off."
Langdon said O'Brien has been an awesome bloke to coach.
"He has been so easy because he soaks everything up."
However their trip to Fiji wasn't easy.
"We were advised before we left by an Auckland promoter that Fiji was like the wild west of boxing. It's just crazy over here," Langdon said.
"Beau had everything against him. Silevini had the home crowd, there were inexperienced referees and officials and Beau had gone up a division against an unbeaten opponent with 11 wins.
"That was the key. This guy did not know how to go backwards. He wasn't expecting Beau to bang him," Langdon explained.
Langdon pointed out there weren't supposed to be standing eight counts but the referee put two on Nawai.
"Silevini was well gone in the fifth round. The first round was even but Beau got better with each round and stepped up a gear. The judges believed Beau had won every round before he got the stoppage."
The former holder of the New Zealand Professional Boxing Association's (NZPBA) light-middleweight title, O'Brien, is enjoying life as a fulltime professional, a lifestyle change he made in December last year after ending a four-year retirement.
During his amateur career, O'Brien, a father of two won 10 of his 20 fights and in 2007 he won the national 69kg welterweight title. The previous year O'Brien was second in the 66kg light welterweight class at national level.