Shares of Freeport-McMoRan (FCX) - Get Report are down nearly 8% Tuesday after analysts at Citigroup downgraded the stock to sell, based on a $4.50 price target. 

The stock has been "sneaking up," climbing a robust 43% in the five sessions before Tuesday, TheStreet's Jim Cramer, co-manager of the Action Alerts PLUS portfolio, said on CNBC's "Stop Trading" segment. 

Cramer cited recent comments from United Technologies' CEO Greg Hayes, which should dissuade investors from wanting to be long copper-related stocks like Freeport. 

Basically, investors buying Freeport are betting that -- among other commodities like oil and gold -- copper prices are going to rise. 

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Freeport-McMoRan FCX data by YCharts

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Not so fast, says Cramer. Freeport has already had a huge rally over the past few days, and he does not want to be involved in the stock. 

"I think this call makes sense," Cramer said of Citigroup's downgrade. Freeport, while not alone, has had to resort to selling assets near the lows. As all investors know, buying high and selling low isn't exactly a recipe for success.

At the time of publication, Cramer's Action Alerts PLUS had no position in companies mentioned.