Investors in Stitch Fix (SFIX -5.08%) are likely in for some bumpy trading next week. The online apparel specialist will announce its latest earnings results after the market closes on Tuesday, Sept. 21.

Share prices have trailed the market by a wide margin since Stitch Fix's last report in mid-June. But the good news is that the slump implies low expectations for the upcoming fourth-quarter report.

Let's take a closer look at three things to watch for this time around.

A delivery man dropping off boxes at a home.

Image source: Getty Images.

1. Direct-buy success will be in investors minds

Stitch Fix reported a solid growth acceleration back in June, with sales gains speeding up to 20% compared to 12% in the prior quarter. Wall Street is looking for a third consecutive win this week. Sales gains should increase to roughly 24%, according to the pros. That forecast syncs up exactly with the updated outlook that management issued following its strong showing in the third quarter.

The big question is whether Stitch Fix is still enjoying some of its fastest user gains to date. Customers were attracted to the service for its fresh products and convenient shopping experience. We'll soon learn whether that favorable trend held up through the early summer. CEO Elizabeth Spaulding should have a lot to say about the new direct-buy feature that launched nationwide in early August. That program might dramatically expand Stitch Fix's addressable market, but could pressure its supply chain, too.

2. About those Stitch Fix profit margins

Another pleasant surprise in last quarter's report was profitability, which jumped back near record territory just a quarter after plunging due to shipping bottlenecks and rising transportation costs. Many of its peers have noted continued challenges in these areas recently, though, and Stitch Fix would feel an immediate pinch if they flared up again in the fourth quarter. Shipping struggles would likely pressure sales gains and gross profit margins, in fact.

SFIX Gross Profit Margin Chart

SFIX Gross Profit Margin data by YCharts.

On the other hand, if the merchandise team kept a steady flow of on-trend apparel in stock, as it did last quarter, then investors might be in for a happy surprise here. The long-term relationship that Stitch Fix is building with its clients should result in higher engagement, and margins, over time.

3. Forecasting fiscal 2022: What expectations are reasonable?

The stock price's slump over the last few weeks implies that investors are bracing for a conservative forecast from Spaulding and her team on Tuesday. The company has surprised investors several times over the last two years, with a few great reports being held back by several disappointments.

Stitch Fix has a new CEO now, and ideally, that management shake-up will help with the volatility that shareholders have endured. Spaulding will have a prime opportunity to set realistic, but positive, expectations when she outlines the company's fiscal 2022 forecast.

Heading into Tuesday's announcement, most investors are looking for sales gains to hold roughly steady at around 20% in the next year. But there's plenty of room for the actual figure to break from those expectations, depending on how well Stitch Fix does at pleasing existing customers while winning new ones in demographics like men and kids, and in geographies like the U.K.