September was the S&P 500 index's worst month since March 2020. Investors grew jittery over a possible government shutdown, inflation, and a sluggish economic recovery, leading the index to drop 4.7%. The biggest losers for the month were FedEx (FDX 0.12%), Las Vegas Sands (LVS -0.98%), and Wynn Resorts (WYNN -0.53%).

Could the September slump represent a buying opportunity? Read on to learn whether these three stocks are worthy of a place in your investment portfolio.

A FedEx employee carries a delivery parcel.

Image source: FedEx.

1. FedEx

FedEx was a winning stay-at-home stock in 2020. But its shares plunged by 17.3% in September, as it became clear that the pandemic-related side effects the parcel delivery giant faces -- most notably, a worker shortage and supply chain inefficiencies -- aren't going away anytime soon. Despite growing its revenue by 14% in its first quarter of fiscal year 2022, FedEx still missed earnings expectations for the quarter because of rising costs. FedEx reduced earnings guidance for the remainder of fiscal 2022 and declined to provide guidance for its second quarter. 

But if you're looking for a value stock to add to your portfolio, FedEx could be worthy of consideration. As of Oct. 1, FedEx's one-year forward price-to-earnings ratio is 9.8, compared to 15.2 for rival United Parcel Service. As Fool contributor Daniel Foelber pointed out, FedEx has also significantly improved its balance sheet in the past three years, reducing its reliance on debt. 

It's also important to note that FedEx's challenges are mostly related to broader economic factors than its business fundamentals. Businesses everywhere are grappling with labor shortages, supply chain troubles, and soaring costs.

Even if worker shortages and supply chain bottlenecks ease during the second half of fiscal 2022, as management predicts, FedEx could be in for a difficult peak holiday season. Its plan to hire 90,000 workers ahead of the holidays seems iffy at best, given that FedEx estimates labor shortages cost the company $450 million in earnings last quarter.

While FedEx could be in for a continued rough patch in the next few months it could also benefit from larger long-term trends, like the growth in the domestic and international parcel market. The stock could also be a good bet if you're bullish on overall economic recovery, as people tend to buy and sell more and, therefore, ship more when the economy is strong.

Gambling chips stacked around roulette wheel on a table.

Image source: Getty Images.

2. Las Vegas Sands

Pandemic-related closures were brutal to casino operators like Las Vegas Sands. But the news that pushed Las Vegas Sands shares down 17% in September was largely unrelated to COVID-19.

On Sept. 14, the Chinese government announced a 45-day public consultation period to review sweeping proposed casino regulations for the enclave of Macao, which is widely considered the gambling capital of the globe. The Bloomberg Intelligence Macau Gaming Composite, an index of the city's six major gaming operators, tanked 23% on the news -- its worst single-day drop in history.

Las Vegas Sands was hit especially hard because of its heavy Macao exposure. It sold its remaining two Las Vegas properties in a $6.25 billion deal earlier this year to focus exclusively on Asia. Macao accounted for 66% of the company's 2019 adjusted property EBITDA, which excludes the Las Vegas properties. Singapore, which still has stringent COVID-19 travel restrictions in place, accounts for the other 34%.

The proposed changes in Macao could have far-reaching impacts on casino operators. The rules could change the number and duration of licenses (known as concessions) granted to operators, which are set to expire in June 2022. Other proposed changes include having government regulators supervising daily casino operations and restrictions on the distribution of dividends to shareholders.

To be clear, nothing has been finalized yet, so it's too early to know if the proposed changes will actually take effect. But if they become law, these regulations could substantially impact casino operations. Given Las Vegas Sands' huge stake in the region, its stock seems like a big risk at the moment.

3. Wynn Resorts

Wynn Resorts, which operates two hotel and casino properties in Macao, also saw its shares topple as investors reacted to potential new restrictions. The stock ended the month down 16.1%, faring slightly better than Sands Las Vegas.

Wynn's Macao properties accounted for nearly 46% of operating revenue in its second quarter of 2021, with the remainder coming mostly from its properties in Las Vegas (35%) and Boston (17%). The fact that just over half of its operating revenue stems from U.S. properties makes Wynn stock somewhat less risky compared to Las Vegas Sands. Gambling revenue has rebounded at a much faster pace at U.S. casinos compared to Macao, where many COVID-19 restrictions remain in place.

But Wynn's substantial Macao exposure still makes it a big bet, particularly in the short term. If you don't have the stomach for big risks, it's worth sitting on the fence until there's more certainty about what the future looks like for casino operators in Macao.

Should you buy on the dip?

Even when you're buying a downtrodden stock like FedEx, Las Vegas Sands, or Wynn Resorts, only do so if you have a strong investment thesis. That means you should have a solid case for why the stock is a good value or has strong growth potential, and understand how it can deliver strong returns for you, as a shareholder.

Each of the three worst S&P 500 performers in September could represent a buying opportunity for the right type of investor, though FedEx certainly appears to be a much safer play than Las Vegas Sands and Wynn Resorts. All three companies face significant uncertainty in the months ahead, so only invest if you're OK with short-term volatility.