Shares of Goldman Sachs (GS) - Get Report are heading for a soft finish to the week. The stock is off 1.2% Friday and one of the weakest members of the Dow Jones Industrial Average.

This weak action has dropped the stock back down to its September lows. A clear break of this area could open the gates to a deep selloff in the near term.

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During the Brexit panic, Goldman Sachs fell to new 2016 lows. After piercing the initial yearly low set back in February near $139, the stock mounted a furious rebound. Three weeks later, shares had gained over 17%, a move that carried the stock all the way back up to its 200-day moving average for the first time since November of last year.

GS remained below this heavy overhead resistance area until an Aug. 15 breakout. The stock trended higher for the next four weeks, but it was clear that momentum was easing. Following the slight pullback two weeks ago, a rather ominous topping pattern is now beginning to form. For patient investors, the result could be much lower entry opportunities.

As this week comes to a close, GS remains range-bound. A close below the $164 will likely end this narrow action with a downside resolution. Investors should keep a close eye on this level, which includes both the July high and 50-day moving average. If this key support zone is taken out, more downside is ahead. Initial support is in place near the $160 area. A fresh base here, which would be a retest of the 200-day moving average, would offer a low-risk entry opportunity for this B+-rated stock.

Disclosure: This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.