The Brazilian left Chelsea on Sunday after his contract expired and he has since agreed terms with Arsenal on a three-year deal worth around £100,000-a-week.
Willian has undergone his medical with the Gunners and a deal to take him to Emirates Stadium is close to completion.
Joorabchian refused to confirm if his client was off to Arsenal, but he did reveal an announcement about the 32-year-old's next club is due soon.
“He is a free player. He had a fantastic seven years at Chelsea,” Joorabchian told talkSPORT.
“He has been under various managers, he has won multiple trophies. He had a fantastic relationship with Frank [Lampard] and he respected Frank a lot.
“But like every cycle, I think that particular cycle has come to a moment where it is a good moment to leave.
“At the moment, just for now, I can’t say where he is going to go. It won’t be long before we announce it. We know where he is going.”
Another winger who has been linked with Arsenal is Sporting Lisbon's teenage star Joelson Fernandes, who is also a client of Joorabchian’s.
But the agent said: “He is a young phenomenal talent, but we have never, ever spoken to him about Arsenal.
“I have probably seen 25 articles about him and Arsenal. It is so untrue because Arsenal have never even spoken about him.
“We haven’t even mentioned him to Arsenal.”