Paulson's Gold Fund was down about 24 percent last year. (Read More: One-Time Hedge Fund Wiz Faces Second Abysmal Year)
Recently, some of Paulson's top gold stocks have been hitting new lows on high volume, O'Brien said, such as AngloGold Ashanti, IAMGOLD Corporation, and Gold Fields Limited.
In his weekly newsletter, O'Brien wrote, "The number of redemptions Paulson gets will affect the [gold] market in the next few months."
Signs of strength in the dollar are also putting gold prices under pressure, and O'Brien told CNBC he expects that to continue.
"We're at $1,660 [on gold prices], we're going to go to $1,550," he said, adding that the market is still in the midst of a two-year consolidation process.
(Read More: Bulls Fret Gold Rally May Be Done)
But when those lows are achieved, prices should really pop, he said. "$2,250, like two or three years from now, might not be a big deal."
Another factor adding to O'Brien's bullish long-term outlook: "Gold has got it's place back in allocations models" among big funds, and he said he thinks that's "not going to leave."
—By CNBC's Matthew J. Belvedere; Follow him on Twitter