Billionaire John Paulson can trace his loss of assets and senior executives to a familiar refrain: poor performance.

Paulson is now re-focusing his firm on his founding strategy -- merger arbitrage -- despite some disastrous returns in recent years. The Paulson Partners Enhanced fund, which uses borrowed money to double down, sunk 23 percent in the first two months of 2018, according to a person familiar with the matter, after plunging about 70 percent over the past four years.

The losses come amid a fund revamp at Paulson’s namesake firm, once one of the biggest in the industry. It will return money to investors in some funds including the Credit Opportunities, Bloomberg News reported Friday. Investors in that credit fund can transfer their capital to a separate pool or they’ll be forced to redeem.

It’s a sobering turnabout for Paulson, who shot to fame and fortune a decade ago with a dramatic, winning bet against the U.S. housing market. But after a series of missteps, the firm’s assets under management have dwindled to about $9 billion from a $38 billion peak in 2011. Most of what’s left belongs to Paulson himself.

Paulson’s share of the firm’s funds has grown in recent years as investors left and performance in several funds suffered. Paulson’s capital, and that of his internal staff, made up 90 percent or more of at least five of the firm’s funds, Bloomberg has reported. The funds affected by the current changes predominantly manage his personal money.

A couple funds are making money this year: Paulson’s Pure Spread fund, which makes less volatile bets around only announced deals, and the European Event Equities fund are both up 3 percent in the first two months of the year, another person said.

The question now is whether Paulson, 62, will ultimately shut his firm to outside investors altogether. For now, there are no immediate plans to turn the firm into a family office, people close to Paulson say. Instead it’s banking on distressed debt and merger arbitrage strategies.

A representative for the firm declined to comment about changes to the funds.

Losing capital may make it harder for the firm to operate and pay staff. The company last week let go of its head of trading, Keith Hannan; head credit trader, Brad Rosenberg; and partners Victor Flores and Allen Puwalski. The cuts add to a slew of layoffs that had already shrunk staff to 95 people down from 128 in 2016.

“We are rightsizing the firm to focus on our core expertise in areas that are growing,” according to a statement Friday from the hedge fund about the layoffs.