"Entourage" star Jeremy Piven ended his run in Broadway's "Speed-the-Plow" after missing two performances citing a mysterious health condition.

The 43-year-old, who had been expected to play producer Bobby Gould in the Broadway revival of David Mamet's 1988 dark comedy "Speed-the-Plow" until late February, missed two recent performances - on Tuesday evening and on Wednesday - angering the attendees. The hard-partying star suddenly quit his role three months early claiming he had mercury poisoning and his doctor ordered him to take a break. 

Needless to say, David Mamet was pretty pissed at the actor's excuse who said he had spoken to Piven on the phone, and he told him he discovered that he had a very high level of mercury.

"So my understanding is that he is leaving show business to pursue a career as a thermometer," Mamet told Daily Variety, "The good news is some really great actors will be helping out and stepping in, which to me is a sign of great heroism and friendship."

Best known for his Emmy-winning supporting role as brash Hollywood agent Ari Gold in HBO's hipster comedy "Entourage," Piven signed on to the show in April 2008.

The new production, staged by frequent Mamet director Neil Pepe, also features Elisabeth Moss of AMC's "Mad Men" and Broadway star Raul Esparza, last seen in "The Homecoming" and robbed of a Tony Award for 2007's "Company."

The play, which focuses on two high-powered Hollywood executives, Charlie Fox and Bobby Gould, who have come up from the mailroom together, received rave reviews in London, where Kevin Spacey and Jeff Goldblum, played the leads. It last hit Broadway in 1988, when it was nominated for a Tony Award, with Madonna playing the female lead Keren.