Springbok fly-half Elton Jantjies, who early this week was sent home from Argentina ahead of a Rugby Championship match, said on Friday that "I let myself...down" but denied having an affair with the squad's dietician.
"I am aware that newspaper articles about my recent behaviour caused a lot of disappointment, distress, and anger to many people, and I apologise unreservedly to everybody I hurt or disappointed, my teammates, the Springbok management team, and SA Rugby," he wrote in a statement.
Jantjies, 32, said he "did not do the Springbok jersey - a jersey that I revered since I was just a little boy - proud"
"I sadly let myself, my family, and the rugby-loving people of this country down, and I deeply regret my actions".
"I take full responsibility for my actions, and I am serious about doing everything in my power to change my behaviour," he said.
South African media last week reported Jantjies, who is married, spent time at a guesthouse with a woman last month, as the team was in Mbombela, South Africa, to play New Zealand.
But he denied that he was with dietician Zeenat Simjee.
"Simjee was never with me at either of the two guest houses that I stayed at. She is a good friend and nothing more," he said. "That her good name is now being dragged through the mud is a shame".
In a separate statement issued at the same time, Simjee said she was with her parents dealing with a family bereavement during the weekend the team was preparing for the Test against Argentina.
"So, the allegations of me spending time with Elton Jantjies at a guesthouse is devoid of any truth," she said, adding she was "shocked" and "devastated" that a local newspaper could "publish such damaging allegations on false and baseless hearsay. It is disappointing".
The Springboks are due to play Argentina on September 17 in the Rugby Championship.
In May, Jantjies was arrested on charges of malicious damage to property of an airline he had flown with from Dubai to Johannesburg.
The case against him was provisionally withdrawn in June.
Jantjies made his professional debut in 2011 with the Johannesburg-based Lions and was loaned to French Top 14 club Pau in 2021 before joining Japanese outfit NTT Red Hurricanes this year.
He also apologised to the management and squad of the Red Hurricanes.