The two men have been at each other's throats over the R&B star's sexual abuse case; Greenberg representing the singer, Avenatti representing a number of alleged victims, parents and whistleblowers connected to the case.
Greenberg told TooFab exclusively on Monday following the shock news of Avenatti's arrest that he was serious about taking on his rival's case - as long as there was no conflict of interest.
He even offered some free advice for the embattled lawyer: “If you're going to war with everyone you better make sure you're squeaky clean," he told TooFab.
"File your taxes on time," he added, "if you're going to sue the President."
Avenatti found himself in the middle of a legal hurricane on Monday, accused of attempting to extort up to $25million from Nike, submitting false tax returns, and illegally siphoning off money from a client's settlements.
Just days earlier his ex wife Lisa Storie had accused him of withholding $2million worth of spousal and child support for his four-year-old son. Avenatti told us last week that was false.
Also in the week before his arrest, Avenatti had announced he was dropping as a client Stormy Daniels, the porn star who claims to have had an affair with President Donald Trump.
Because I don't hold grudges I am happy to offer #Avenatti My legal assistance since I hear he needs a good lawyer