Slow is the new fast when it comes to economic growth.

While the Schwab IMPACT 2015 conference opened with rays of optimism, two eminent fund managers doused attendees with cold water Wednesday afternoon.

Jeff Gundlach, CEO and co-founder of DoubleLine, questioned whether the financial industry was ready for a potential interest rate hike in December.

“Two-thirds of today’s money managers have never experienced a single Fed rate hike,” Gundlach says. “If rates go up, one day later we'll be talking about another raise. Borrowing costs will go up on leveraged portfolio, and everybody has to get small, all at once.”

Continuing an argument against rate hikes he started making in the summer, Gundlach says economic conditions still do not merit a raise.

“We saw the stock markets swoon pretty badly in August and September, and they’ve fully recovered in the U.S. and other places,” Gundlach says. “The credit market, though, is not showing the same green light signals about a strengthening economy.”

He even holds out the possibility of negative interest rates.

"I always thought negative interest rates were impossible, but that's where we are," Gundlach says. "If it happens, go borrow an infinite amount of money on negative interest rates."

While some indicators have turned positive, including an impressive October jobs number, other indicators are flat.

“Real GDP isn’t going up,” Gundlach says. “The GDP forecasts get lower every year;, what you’re seeing is a triumph of hype over experience. There’s not enough GDP to go around. Nominal GDP has decreased after it peaked in the early 1980s. 2015 will be the second largest contraction of global GDP. There isn’t GDP to go around.”