Investing.com -- Trend-following funds are set to become a headwind for equities, with Goldman Sachs' trading desk modeling commodity trading advisers to sell stocks in every scenario over the coming week.

Goldman said CTA buying had provided consistent support to the market in recent weeks, but that demand has now dried up.

"CTA buying gave the market a clear source of demand for a few weeks, providing a consistent layer of support, thus allowing for a temporary green light to chase the rally," Goldman traders, including Gail Hafif, reportedly stated.

The S&P 500 is currently 3.8% and 4.8% above its short- and medium-term thresholds, respectively, levels Goldman said are likely to trigger up to $50 billion in selling as funds move to flatten exposure.

The shift follows an unusually rapid repositioning earlier this month, when systematic funds moved from short to long U.S. equities in near-record time.

"The one-month change in US positioning across the major systematic cohorts is the 2nd largest re-leveraging in our dataset going back to 2016," the Goldman desk wrote.

The bank adds that systematics have purchased nearly $80 billion in U.S. equities over the past month, leaving CTAs currently long $44 billion in U.S. stocks.

Goldman also flagged that the broader systematic cohort experienced massive positioning changes earlier in April, and that the swift reversal from short to long now sets the stage for potential selling pressure ahead.