Bryn Mawr's Jeffrey Mills believes there's a high probability the low is in for the market.
But he also warns stocks won't see a sustainable rally until there's a way to fight coronavirus infections.
"We just don't know how long the economy is going to be shut down," the firm's chief investment officer told CNBC's "Trading Nation" on Friday. "We don't know how long folks will be quarantined, and I think because of that, it's going to be very difficult for equities to move higher in a steady fashion at least over the next couple of months."
Mills, a CNBC contributor, notes Wall Street is already pricing in virus aid from the government and Federal Reserve. So, the only key upside catalyst left, according to Mills, is a meaningful advancement in treating coronavirus.
"The fact that the Fed is now here and they're supporting the credit markets… effectively puts a little bit of a bottom in the market," he said.
Mills, who has $16 billion in assets under management, isn't ruling out any new market jumps either.
If the S&P 500 surges another 10%, he plans to take profits.
"We would use a rally up into the 2,800 level in the S&P 500 as an opportunity to take some risk off the table. Just from a technical perspective, 2,800 is around where resistance is," Mills said. "That's the 50% midpoint between the all-time high and the recent low."
He contends emotions — not fundamentals — are driving the market's wild swings.
"The blind spots that we're facing in terms of the contraction in GDP and the contraction in earnings are large enough that investors just don't know what the right price is in terms of the most probable outcome over the next couple of quarters," he added.
Despite his market warning, Mills sees pockets of opportunities.
He sees two unpopular spots during the recent bull market as portfolio protection plays: Mid and small cap value stocks.
Mills builds his case on trends that emerged in the aftermath of the tech bubble, financial crisis, 2011 Euro debt crisis, 2016 oil crash and the 2018 flash crash sell-off.
During those periods, he said mid and small caps outperformed large caps while value outperformed growth stocks over the 12 months after the market bottomed.
So, now may be a good time to consider adding exposure.
"The value differential between value and growth is so stretched in favor of value, and small caps have been so oversold," Mills said. "It could be the perfect time if you're underweight these areas in your portfolio to start to add a little bit of exposure there."
VIDEO7:2007:20Coronavirus clarity needed for sustainable market rally: Bryn Mawr's Jeff MillsTrading Nation