What's your best strategy when it comes ot Best Buy (BBY) - Get Report ? Think about selling ahead of its fiscal 2017 first-quarter earnings early Tuesday.

Why? The big box electronic retailer's technical chart shows that while Best Buy is improving sales, you should sell and wait for a 7% pullback in the stock.

BBY stock closed Friday at $32.34 up 2.57%. The shares are up 6.2% so far on the year, including a 4.5% rise in just the past five days. BBY is cheap, trading at just 11 times forward estimates, compared to a forward price to earnings multiple of 17 for the S&P 500 index.

But the market doesn't believe in Best Buy's fundamental improvements. BBY stock shows a decline to back to $30 per share is imminent. See the chart below, courtesy of TradingView.

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The chart shows -- between the two blue arrows -- how BBY stock has traded in a tight range between $30 and $33 over the past three months. The stock last week reclaimed both the 50-day and 20-day moving averages, which both now meet at $32 per share. During that span, BBY stock has established support, which is now firmly set at around $30 per share (yellow arrow).

But to avoid falling below support, or a 7% decline, Best Buy not only needs a beat on Tuesday's earnings, it must also deliver solid same-store sales growth. Analysts see the company earning 35 cents a share on $8.3 billion in revenue, declines of 5.4% and 3.1%, respectively, over the previous year period.

Best Buy must also raise guidance. That's a tall order, especially in the face of Amazon.com's (AMZN) - Get Report online dominance. In Best Buy's fourth quarter, same-store sales declined 1.7%. This was partially offset by 13.7% rise in domestic online revenue.

Given the punishment retailers have taken so far for weak comps, it would be a mistake to risk a disappointment with BBY, especially with the shares having already outperformed the market year to date. This means there are now likely more net sellers than there are buyers.

If its earnings don't meet or beat expectations, BBY will struggle to hold support at $30, meaning it could retest its February low at around $26.50.

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