"He denies any allegations of wrong doing. He's going to ride out this process and clear his name." Mr Porter told RNZ that Muliaina was also worried about how the allegation would impact those who were close to him.
Inspector Andy Walbeoff, of South Wales Police has said the alleged victim was a 19-year-old female, who was local to the Cardiff area.
He was unable to confirm where the alleged assault took place, as it could "compromise further witnesses". The alleged incident occurred in the first week of March, Mr Walbeoff said.
Mils Muliaina has since been bailed after being arrested on suspicion of sexual assault, according to The Irish Independent.
"The man has been handed over to officers from South Wales Police who are investigating the incident."
"He has been released on police bail pending further investigation."
Mils Muliaina was downing Red Bull and double vodkas with teammates until 3am at an ex-pat bar in the Welsh capital of Cardiff on the night he is alleged to have sexually assaulted a woman.
The former All Black great and teammates from his Irish club team Connacht then left Kiwis bar for a nearby nightclub.
The night out followed the side's controversial 18-17 loss to the Cardiff Blues at Cardiff Arms Park on March 6.
"They were drinking quite a bit," a worker from Kiwis told the Herald on Sunday last night.
"They were in a really good mood, they were quite chirpy. As far as we were concerned they were delightful people to have in - really friendly, really approachable. A few of them were quite oiled up."
In the rugby-mad country, a few post-game drinks are par for the course and Connacht manager Tim Allnutt confirmed the team had all been drinking at the venue.
The Kiwiana-decorated bar is a popular haunt of expats in Cardiff and it stocks Steinlager and New Zealand wines.
The bar worker said the Connacht contingent remained at Kiwis until its 3am closing. Players then moved on to the Karma nightclub, which stays open until 6am.
He saw Muliaina and coach Pat Lam talking in the middle of a road while the remainder of the group went ahead. "They were just talking, they were quite calm," he said.
Photographs posted on Kiwis' Facebook page show Muliaina and Lam happily posing with bar staff and revellers.
The photos have been posted to Facebook and state Muliaina was "enjoying a few" that night.
What happened over the next few hours is now the focus of a police investigation into Muliaina.
At the time of going to print, no charges had been laid and he was being questioned at South Wales police station after spending the night there.
It is understood friends and family had not heard from him as his mobile phone had been seized.
Muliaina's manager, Simon Porter, told the Herald on Sunday he knew nothing about the allegations but Connacht Rugby Club had organised a lawyer for him.
Porter said he had not been able to speak to Muliaina since he was taken into custody.
"I'm shocked. Everyone's just trying to get information. You just want to find out more information but we are only getting tidbits."
Rob Nichol, chief executive of the New Zealand Rugby Players' Association, last night said he was stunned at Muliaina's arrest.
He had been in contact with Porter and was confident the rugby hero would get all the support he required.
"But until you learn more it's hard to know where to target support. We'll see how things pan out."
He said it was important people didn't "pre-judge" Muliaina's plight. "In the fullness of time things will come out and people can make their own judgments."
Muliaina's family would not comment when contacted by the
Herald on Sunday
yesterday.
He has split from his wife Hayley Muliaina and she was not at the Grey Lynn home she owns with him.
The Muliainas' son, Max, 6, was only three days old when diagnosed with a hole in his heart and spent time at Auckland's Ronald McDonald House while he underwent numerous surgeries.
Muliaina's arrest yesterday came as a shock to everyone who knows him as a devoted father and rugby legend.
"He's done such a great job here. He's done such a great job for the young lads," said Irish journalist Linley Mackenzie.
Muliaina played 100 tests for the All Blacks between 2003 and 2011.
Inspector Andy Walbeoff, of South Wales Police, confirmed no charges had been laid against him by press time.
Walbeoff confirmed Muliaina was the only person being spoken to in relation to the alleged sexual assault. "Sexual assaults, no matter how minor or major the sexual assault, we have to investigate them properly."
Walbeoff declined to comment on why police waited for him to arrive back in the UK from Ireland before he was arrested.
"There is rhyme and reason behind it but it would be wrong of me to comment at this time."
Gloucestershire Police last night confirmed an arrest had been made. "A man in his 30s was arrested at Kingsholm Stadium tonight [Friday, April 3] on suspicion of sexual assault in relation to an incident in Cardiff in March.
Connacht Rugby issued a statement to media to confirm Muliaina was assisting South Wales Police with inquiries.
He joined Connacht last year, and announced earlier this week he would be leaving for Italian side Zebre at the end of the season.
That future is now in doubt as police examine his past.
• On March 6, Mils Muliaina lined up for Connacht in their Guinness Pro 12 clash against the Cardiff Blues in the Welsh capital. Connacht lost 18-17.
• The next day, Kiwis Bar & Club in central Cardiff posted photos of Muliaina with coach Pat Lam and other Connacht squad members enjoying a night out at the venue.
• Muliaina was then sidelined for three weeks with a hamstring injury.
• On Wednesday, it was confirmed he would leave Connacht after signing a one-year deal with Italian club Zebre.
• Yesterday, he returned to the field during Connacht's 14-7 European Challenge Cup semifinal loss to English club Gloucester at Kingsholm Stadium. Muliaina limped from the field injured during the first half.
• After the game, he was seen talking and laughing with fellow former All Black John Afoa, who plays for Gloucester.