FedEx's earnings report on Tuesday afternoon could mean major moves for its stock.

The options market is implying a 5% move in either direction for shares of the shipping giant following its earnings report after the closing bell.

That implied swing doesn't seem unusual for FedEx, which has moved 6% on average after its last four earnings reports. But this time, there's a key support level in play that could make for an especially risk-averse trade.

"All four times over the last year, this stock has declined the next day" after earnings, Dan Nathan, co-founder and editor of RiskReversal.com, said Monday on CNBC's "Options Action." "This stock has been a sale on rallies, but it does find buyers because of that fine management and that cheap valuation."

This time brought about some bearish bets. When FedEx's stock was above the $161 level on Monday, several traders bought $160/$150 put spreads expiring on June 28 for $3 each, betting that FedEx's shares would decline to about $150.

That would be roughly in line with the options market's implied move for FedEx, but there's another, more interesting reason why the $150 level is so critical for this stock, said Nathan, who also appears regularly as a trader on CNBC's "Fast Money."

"One hundred fifty dollars could be a very important level," Nathan said, pointing to FedEx's one-year stock chart. "This is the December low just above $150. Last month, it kind of bottomed out just about $150. Now it's kind of turning lower as we head into earnings."

Now, having lost nearly 33% in the last 12 months, FedEx is back at its recurring floor of support of $150, the trader said.

"It's right at that trendline," he said. "I would say $150 is a very, very important level. I'd just make one point: I think expectations are very low, so this company does not have to put up a big number for it to find some support down in the $150s."

FedEx shares lost 2.4% in Tuesday morning trading. The stock is up more than 2% this month, but still struggling to make year-to-date gains.

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