Moss Slams Piven as 'Unprofessional,' Stars Feuding?

Elisabeth Moss blasted fellow actor Jeremy Piven as being "highly unprofessional" during a live interview this week.

The "Mad Men" star and Piven, best known for his role on HBO's "Entourage," both appeared in the Broadway show "Speed-the-Plow."

During an episode of Bravo's "Watch What Happens Live, " Moss had no problem voicing her opinion her former co-star, who abruptly exited the 2008 Broadway show.

"That's a very good one," the actress said when asked about Piven's departure from the show.

"I could go on and on," she said before citing his "highly unprofessional" behavior.

"We were all surprised," Moss continued. "It came out of nowhere. He just didn't come back one day."

At the time, Piven blamed his departure from "Speed-the-Plow" on mercury poisoning from "eating too much sushi."

Moss' comments leave fans wondering if she and Piven feuded while on the set of the Broadway show. The actress made no further comments on the situation.

Moss stars as Peggy Olson on "Mad Men" alongside Hamm, January Jones, Christina Hendricks, John Slattery, and many more. The drama series is in its sixth season.

In the past, "What What Happens Live" has seen stars "plead the fifth" where they refuse to comment on certain topics.

Similar to Moss, Nick Lachey did not opt to plead the fifth during a recent appearance on the Andy Cohen-hosted television series.

After revealing that he had not spoken to ex-wife Jessica Simpson in six years, the 98 Degrees singer commented on his former father-in-law Joe Simpson.

"The best thing about not having Joe Simpson anymore as a father-in-law is I don't have to play grab-a-- under the table on Easter Sunday," said Lachey, referring to the rampant rumors that Simpson is gay.

"It may not be [funny] tomorrow, but it is tonight," Lachey added of his sharp comment.

"Watch What Happens Live" airs on Bravo Sunday through Thursday at 11 p.m. EST.