WITH AN EYE ON . . . : ‘Ellen’ gets a shot of testosterone that goes by the name of Jeremy Piven

Although Jeremy Piven sighs, “I couldn’t be more single,” “Ellen” producers say his “charismatic, sexy maleness” breathes energetic life into their ABC sitcom.

Piven’s arrival on the show’s third season marks a complete cast change, save for its irrepressible and likable star Ellen DeGeneres.

“Jeremy adds this great urban energy and great maleness ,” executive producer Eileen Heisler explains. DeGeneres effectively plays off Piven’s manic energy in a way the star couldn’t with other co-stars, Heisler says. By bringing on Piven as Spence Kovak, Ellen’s East Coast cousin who dropped out of medicine, “the ensemble is stronger.”

The 30-year-old Piven had just come off of NBC’s failed “Pride & Joy” when Spence was created for him. Although he was offered his own show, Piven took “Ellen” and the potential for as much improv as on “Pride & Joy.”

“I think the writing’s really great and I’m having a blast,” says Piven from his Hollywood home, the noise of traffic whooshing in the background. He’s sitting on his front porch because he wants to “pretend we’re somewhere in the Midwest, where we always sit outside.” But when the Evanston, Ill., native’s voice is barely audible over the cars, he sighs, “fine,” and walks into the house. Still talking.

Talking is where Piven has been most impressive. Both the actor and Heisler mention his role in this year’s “Miami Rhapsody” as integral to his landing the role on “Ellen.”

“They liked the spirit,” he says of his “Miami Rhapsody” role, a dentist who seems unlikely to woo Carla Gugino’s character but does so with surprising finesse. Heisler says the role “really opened our eyes to what Jeremy could do.”

One thing Piven can do is talk a mile a minute. Check out most of his 20-odd feature roles (yes, there have been that many). They are “that manic, fast-talking, articulate presence,” the actor says.

Piven’s first role in 1986’s “Lucas” was followed by “One Crazy Summer,” “Say Anything,” “The Grifters” (the latter three with childhood pal John Cusack), “The Player,” “PCU,” and “Judgment Night.”

On television, Piven was a regular on Carol Burnett’s 1990 variety show for NBC, “Carol & Co.,” and on HBO’s “The Larry Sanders Show” as one of Larry’s original head writers.

The snappy comeback guy may be Piven’s most familiar character, but audiences soon will get doses of different Pivens. During the summer, the actor worked on four features.

The day after “Pride & Joy” stopped production, Piven began the Brooklyn slacker comedy “Layin’ Low.” He followed that up by playing a gangster doctor in the Robert DeNiro-Al Pacino film “Heat.” The black comedy “Livers Ain’t Cheap,” with Gary Busey and Emily Lloyd, was next. His last film of the summer stars Bill Murray--”the Man,” Piven calls him--in “Larger Than Life.”

Piven, who still maintains the five best friends he met in junior high, began acting at 8 at his parents’ acclaimed Chicago-based “Piven Theatre Workshop.”

Acting “was amazingly fun and worked out well,” even though he never had any parental pressure to become an actor, says Piven, who notes that his occasional real-life seriousness often surprises new acquaintances.

The actor studied drama at NYU, Drake University and the Eugene O’Neill Theater Center, as well as the National Theater of Great Britain. “I was just a biscuit away from becoming a professional student,” he jokes.

But, as Heisler says, “He’s just got that sexy charisma about him that both men and women respond to. He’s just so quick and funny and goes totally out on a limb.” So Piven worked steadily.

Now, he and Cusack will revive their originally Chicago-based experimental New Criminals Theater Company in Los Angeles, giving Piven yet more work.

While he hopes to eventually write, direct and produce, Piven, for the moment, is getting ready for the weekend, to take on a “little role” in Ben Stiller’s “The Cable Guy.” “Hey,” Piven says in his mock-serious tone, “I’m always ready to play.

“I don’t have a girlfriend. I don’t even have a plant,” he muses. “I guess I have a career.”

“Ellen” airs Wednesdays at 8 p.m. on ABC.