(Check out Carter’s worthcharting.com for actionable recommendations and live nightly videos.) Here’s a brief examination of key downside levels for the SPDR S & P 500 ETF (SPY). In the context of the current sell-off in the market (the SPY at its low today is -3.16% from Thursday’s all-time high of $639.85). Support comes into play (begins) at pre-tariff sell-off all-time high of Feb. 19 at roughly the $631 level. A drawdown to said level would represent a 4.1% decline from Thursday’s all-time high. Importantly, support is not a plywood board or a concrete floor, but rather is a mattress top. Support begins at the $631 level, and as is so often the case when a stock, index, currency or commodity sells off to support, said securities will sink into support before finding support (will sink into the mattress further). In fact, support comes into play all the way down to around the $575 level. See second chart below. A drawdown to said level would represent a 10.10% decline from Thursday’s all-time high. Meanwhile, the mid-point of support comes into play at the $593 level. A drawdown to $593 would represent a 7.25% decline from Thursday’s all-time high. Bottom line, the current sell-off is a mere 3.16% and a mere 2 days in duration. We would anticipate further downside in the days/weeks ahead and would take measures accordingly. DISCLOSURES: None. All opinions expressed by the CNBC Pro contributors are solely their opinions and do not reflect the opinions of CNBC, NBC UNIVERSAL, their parent company or affiliates, and may have been previously disseminated by them on television, radio, internet or another medium. THE ABOVE CONTENT IS SUBJECT TO OUR TERMS AND CONDITIONS AND PRIVACY POLICY . THIS CONTENT IS PROVIDED FOR INFORMATIONAL PURPOSES ONLY AND DOES NOT CONSITUTE FINANCIAL, INVESTMENT, TAX OR LEGAL ADVICE OR A RECOMMENDATION TO BUY ANY SECURITY OR OTHER FINANCIAL ASSET. THE CONTENT IS GENERAL IN NATURE AND DOES NOT REFLECT ANY INDIVIDUAL’S UNIQUE PERSONAL CIRCUMSTANCES. THE ABOVE CONTENT MIGHT NOT BE SUITABLE FOR YOUR PARTICULAR CIRCUMSTANCES. BEFORE MAKING ANY FINANCIAL DECISIONS, YOU SHOULD STRONGLY CONSIDER SEEKING ADVICE FROM YOUR OWN FINANCIAL OR INVESTMENT ADVISOR. Click here for the full disclaimer.