J.J. Kinahan, chief strategist at TD Ameritrade, said the correlation between oil and stocks did seem to be moving apart.
"It was 92 [percent] near the end of last month and today it was around 83," he said. Kinahan said traders were watching the $35 level but the correlation could make a strong return if oil moved to $32.
"I think this week to me is a time to make our game plan for the rest of the quarter. I think it's one of the reasons the volume was a bit light last week and maybe a bit light this week," Kinahan added. "The Fed minutes don't tell any great story but there is some risk there."
The minutes of the Fed's latest meeting will be released Wednesday, and will be important after Fed Chair Janet Yellen delivered a dovish speech that pushed back market expectations for rate hikes.
"I think what you saw today was people cleaning up risk and taking off things they thought performed pretty well since mid-February. They're thinking about what they're going to rotate into as they head into the rest of this quarter and year," said Kinahan.
He said energy and consumer staples had been attracting buyers. Healthcare, meanwhile, was a wild card because both Republican front-runner Donald Trump and Democrat Hilary Clinton have said they would go after drug prices.
Kinahan pointed to Monday's 7.8 percent jump in the Volatility Index, or VIX. The VIX is the market's fear gauge, based on puts and calls on the S&P 500, and it has been at a very low level recently.
Bonds were also moving higher, with the 10-year yielding moving inversely lower to 1.77 percent.
"If gold had moved higher too, I would have said this is not a good sign" for stocks, said Kinahan.