Washington said in a statement that "this is a legal matter and I am limited in what I can say other than that my lawyer and I will continue to cooperate with investigators and welcome the opportunity for all the facts to be presented.
"I regret that the situation has brought this kind of attention to my family and my team. I look forward to resolving it as soon as possible," added Washington, a former second-round draft pick who was a Pro Bowl alternate last season.
The Cardinals said in a statement before Washington was arrested that "these are serious accusations that we are closely monitoring. Until all the facts are determined and out of respect to the process, we will decline any further comment at this point."
Washington led the Cardinals with 134 tackles — 108 of them solo — and nine sacks last season and signed a six-year contract extension in September.
He was suspended for the first four games of the 2013 season for violating the NFL's substance abuse policy.