His attorney said the 25-year-old Sonics forward will enter an Alford plea -- meaning he doesn't admit guilt but believes a jury likely would find him guilty.
The charging papers by the King County Prosecutor's Office say the incident happened in Patterson's Bellevue home last September.
His 24-year-old nanny says Patterson's wife was away from the home. The nanny says she walked into the media room of the house and found Patterson standing there naked and masturbating.
She says he ran up and grabbed her from behind, that she struggled with him for a while, and then became afraid for her safety if she continued to fight off his advances.
She says that fearing the assault would continue to escalate, she gave in and performed oral sex on him for "only a few seconds."
Afterward, she says Patterson told her that "everything would be all right if she did not tell anyone what had happened."
The nanny did tell friends and her father the next day.
Through his attorney, John Wolfe, Patterson has denied any criminal wrongdoing. Instead, the Sonic admits to "marital infidelity for which he takes full responsibility."
Wolfe gave KOMO 4 News this statement:
"Ruben Patterson denies that he engaged in any criminal conduct," said attorney John Wolfe. "He acknowledges that he committed an act of marital infidelity for which he accepts full responsibility and would like to apologize to his wife, his teammates and team and the complaining witness for any difficulties that they may have experienced from the result of his mistake. In order to avoid the significant financial and emotional cost associated with a trial on the merits, he has determined that he will enter an Alford plea of guilty to the gross misdemeanor offense of attempted rape in the third degree to bring full closure to this incident."
The incident was first reported last September, the case was forwarded to the prosecutor's office in January, and Patterson was never arrested. Bellevue police say the length of time taken to investigate and to file charges is not unusual.
This isn't Patterson's first brush with the law. He was convicted of assault for breaking a man's jaw outside a Cleveland bar this past summer.
Tuesday afternoon, the Sonics issued this statement by team president and CEO Wally Walker:
"We understand Ruben Patterson will enter an Alford guilty plea to the legal action brought against him in King County Superior Court.
"As an organization, any legal situation regarding an employee, including Sonics and Storm players, is treated very seriously. We will make disciplinary action a priority per our company's policies and guidelines regarding any employee's violation of the law.
"When we first learned of this investigation, we decided not to speak publicly about it. Like the police and prosecuting attorney, we did not want to say anything that could have interfered with a fair trial. Ruben's decision to plead guilty ends that risk. "Ruben has issued an apology. This is an initial step, but we also want to re-emphasize that our organization will impose a disciplinary penalty, should he return to the Sonics next season."
Patterson will become a free agent in July. Walker declined to say what discipline Patterson might face.
On KJR Sports Radio 950, Sonics owner Howard Shultz wouldn't specifically discuss Patterson's future. But Shultz said:
"Obviously we'll have to sit down with Ruben and his representatives. But I've been saying all along that we need to build toward players with character and integrity and this news is not compatible with that."
Patterson is scheduled to be arraigned Friday.