In fact, the divergence between oil and the broad-market index should not be much of a surprise, given that the share of the S&P 500 composed of energy stocks has actually fallen dramatically over the past few years.
In 2011, the energy sector made up about 12 percent of the index. Now, energy stocks make up less than 6 percent of the S&P.
Unsurprisingly, the 100-session correlation between (the daily moves of) oil and the S&P 500 have tumbled to a level that shows almost no real relationship between the two.
The decreasing weight of energy also means that energy's impact on total S&P 500 earnings is significantly diminished, S&P Global portfolio manager Erin Gibbs pointed out Wednesday on CNBC's "Trading Nation."
"Right now the energy sector is expecting about a 300 percent gain in earnings growth for 2017. Even if you wipe out that 300 percent, the S&P 500 earnings expectations only goes down about 60 basis points — so you can just see just how little of an impact that is even with such a big number," Gibbs said.
"For energy to really have an impact on the overall broader market and what kind of earnings growth we're expecting, it just has to be astronomical numbers," Gibbs added. "We're still looking at double-digit earnings growth, with or without the energy sector growing."
Still, Miller Tabak equity strategist Matt Maley points out energy companies have issued "a decent amount" of high-yielding debt.
The popular HYG high-yield ETF has "held up because the exposure on the oil side hasn't been as big" as in the past, "but it's still big and it still will have an impact. And we always know that whenever you have credit markets start to see disruptions, it ripples into many other different markets," Maley said.
If oil "continues to go lower, it's going to cause a lot of problems," he added.