It's the rivalry that will apparently never die.

And also the rivalry that many current television fans likely never knew existed.

On Monday, Isaiah Washington attacked his former Grey's Anatomy co-star, Katherine Heigl, on Twitter for saying he should "never be allowed to speak publicly again."

Washington, who portrayed Dr. Preston Burke on the long-running medical drama, was fired from Grey's Anatomy back in 2007 after using a homophobic slur on set.

He dropped the F-word at the time while arguing with Patrick Dempsey, using it as a negative reference to another cast member, T.R. Knight, who later come out as gay.

Heigl, as many TV fans may remember, also left Grey's Anatomy -- her departure came in 2010 after she publicly trashed the show's writers.

"This woman once proclaimed that I should ‘never’ be allowed to speak publicly again," wrote Washington alongside a photo of Heigl.

"The world agreed with her proclamation back then and protested for my job and my head in 65 languages.

"I wish I was on Twitter in 2007, because I will NEVER stop exercising my free speech."

It's unclear why Washington chose this time to once again go after Heigl.

Way back in 2007, in the Golden Globes press room, Washington told Access Hollywood that he did NOT directly attack Knight for his sexuality.

"No, I did not call T.R. a f----t," he said in his own defense to that outet.

At the time, Heigl responded by saying:

"I'm going to be really honest right now, he needs to just not speak in public. Period."

In another message on Monday, Washington fired back at a follower claiming Heigl was merely defending her gay friend, writing:

"Your opinions are your own, but you are a fool, a liberal and and misguided feminist to even try and defend this woman.

"You weren’t there, so die on this hill, whoever you are. She could have cared less about her gay friend. Chandra Wilson knows all about that too."

Wilson is one of the three original Grey's Anatomy cast members who remains on the series.

Speaking out about his firing, Washington told Entertainment Weekly in June 2007 that he “did everything that the producers and the network asked me to do.

"I came back under great duress and stress, and thought I was doing the job I was hired to do.”

This is kind of true.

Washington was not let go after the initial F-word story went viral; he was only fired after he reiterated the accusation (and that homophobic slur) at the Golden Globes, as we cited above.

Incredibly, Washington returned to Grey's Anatomy  in 2014 for one episode to send off Sandra Oh's character Cristina Yang, whom Burke left at the altar years before.

“It’s important to me that Cristina’s journey unfolds exactly as it should,” creator Shonda Rhimes said at the time about the decision.

“Burke is vital to that journey -- he gives her story that full-circle moment we need to properly say goodbye to our beloved Cristina Yang.”

Heigl, meanwhile, was never invited back to the program as the character of Izzie Stevens.

Of Washington's recent remarks, a source close to Heigl says:

"Katherine stood up for her close friend twice when Isaiah publicly outed him and called him a f----t. That’s hate talk, not free speech.

"She is proud that she stood up for him. Katherine is and always will be an advocate and ally to the LGBTQ community."

This renewed feud comes on the heels of another stunning Grey's Anatomy comeback.

On last Thursday's season premiere, Patrick Dempsey returned in the role of Derek Shepherd.

It was absolutely shocking.

The only thing more shocking would be if Washington and Heigl ever sign on to co-star in a Netflix romantic comedy or something.