The cast of “Shark Tank” is heartbroken over Mark Cuban's decision to leave the hit reality series about business and entrepreneurship.

“It's terrible, like losing a brother. I know I'll get over it; I hope I get over it, but it feels very sad,” co-star Barbara Corcoran told TheWrap. “He feels irreplaceable. They say people aren't irreplaceable, but in the series he is. He really is.”

The Dallas Mavericks co-owner joined the ABC tank as the series' fifth regular investor in Season 3, after original star Kevin Harrington exited after two seasons (in which Cuban appeared as a guest). Since then, the Cuban has been known as the shark, circling the waters waiting to hear everyone else's potential offers before committing to a deal.

Great Shark Kevin O'Leary – or Mr. Wonderful, as he likes to be called – said he knew long before Cuban's announcement that the billionaire would be leaving the program.

“He has talked over the years about how it is very time consuming and takes longer each year. I understand his transition, but he was great to work with,” O'Leary shared. “But the show goes on as usual and I think there are a lot of people who want to be sharks, guest sharks. I think that’s good because I think America needs the show and the show needs America.”

Fellow Sharks Robert Herjavec pointed out that Cuban still has a lot of potential updates to make before he's truly eliminated. “Will he ever leave?” he asked. “Eight thousand investments… there will be updates every week.”

As for Lori Greiner, she said Cuban also confided in her his desire to retire from “Shark Tank.”

“I spoke to Mark about this on and off for several years and when he told me I was heartbroken,” she said. “Honestly, I love and adore him and I really can’t even imagine this show without him. But he will be a dear friend and family for life. But one word: heartbroken.”

As TheWrap previously reported, FUBU founder Daymond John spoke about how casting Cuban saved the show from bankruptcy in the earlier seasons.

“Mark Cuban found out it was one of the top shows for kids and families and said, 'I'm coming for entrepreneurship,'” John explained. “He ran the show on '(Jimmy) Kimmel (Live!)' and '(The) Ellen (DeGeneres Show)' and then the show started to take off.” Mark said: “I'll be a year or two “Stay to help you all.” Mark stayed for 15 years. So it’s just an honor that he’s been such a big supporter of the show and we’re lucky to have him.”

Cuban, who has financially supported 85 companies since joining the “Shark Tank” cast, first shared the news that he was leaving the show while appearing on the sports podcast “All the Smoke” in 2023.

“This is our 15th year. Next year's 16th year will be my last year. So I only have a year left,” he revealed. “It’s time.”

Kind Snacks founder Daniel Lubetzky was promoted to full-time shark investor on the hit ABC series in September.

“Shark Tank” Season 16 premieres Friday, October 18 on ABC and streams the next day on Hulu.