There's a strong possibility that the bullishness that's happening in the markets right now won't last, especially as cases of COVID-19 continue to rise. It's far too early to be talking about a recovery in the economy when the worst may still be to come. A recession's already here, and it's unclear how long or how deep it will be.

But as long as the economy's in a downturn, a market crash is never too far away. And when the markets crash again, whether it's this year or next, there are three stocks I'll be keeping an eye on and potentially adding to my portfolio should they go on sale:

1. One Medical

1Life Healthcare (NASDAQ:ONEM), which is also known as One Medical, began trading on the NYSE on Jan. 31. It's been dominant since hitting the markets, with the stock price up by more than 80% year to date -- well above the S&P 500 which is down 2.2% over the same time period. 

Stethoscope and pen laying on a laptop.

Image source: Getty Images.

What makes One Medical an appealing buy is that the primary care provider offers patients the option of in-person visits or virtual visits. And for a modest annual membership fee of just $199, it's an affordable way for people to access healthcare coverage.

As of March 31, the company boasted 455,000 members. That was a 7.8% increase from Dec. 31, when there were 422,000 members, and a 25% increase from a year ago, when there were 364,000. With the company's low-cost membership and many people out of work, One Medical could see a lot more people signing up for coverage during the pandemic.

Year-over-year revenue growth during the first quarter of fiscal 2020 was also about 25%, in line with member growth. The one negative was that the company's net loss grew from $7 million a year ago to $34.6 million this past quarter. But with a growth company, it often takes time for profits to come, especially for a young organization that's recently become public.

One Medical has a bright future, and the only reason I'm hesitant to buy the stock today is that it's not cheap, trading at more than 12 times book value and 11 times revenue. In March, the stock crashed below $20; if it gets below that threshold again, it could be a steal of a deal.

2. Workday

I've always been a fan of Workday (NASDAQ:WDAY) because I'm a believer in automation and efficiency. The tech company helps its clients manage and optimize various business functions. Workday integrates with many different systems, including Salesforce, which can simplify a company's day-to-day activities and data entry.

Whether companies are looking to get more efficient or trying to push more of their operations to the cloud, Workday can help its customers achieve cost savings. In a recession, bringing down expenses will be of immense importance for companies looking to stay competitive. 

Workday released its first-quarter fiscal 2021 results on May 27. In Q1, its revenue was up 23.4% from the prior-year period. That's down slightly from the 28.5% sales growth that Workday achieved in fiscal 2020. Like One Medical, Workday's struggled to stay out of the red; It's posted a net loss in Q1 and in each of its last 10 quarters.

This also isn't a cheap stock, as shares of Workday trade at 17 times book value and 11 times revenue.

In March, the stock fell to $107 per share, nearly half its price today. In the past 12 months, it's been rare for the stock to even trade below $130. And that's why if there's a crash in the markets, it could be a great time to load up on shares of Workday as it may be one of the few times to grab the stock at a discount.

3. Dollar Tree

Dollar Tree (NASDAQ:DLTR) is another attractive stock to keep an eye on. The reason I like this stock is that dollar store chains are fairly resilient during a recession. As purchasing power declines in an economic downturn, cutting expenses becomes more important for consumers, which could lead to more traffic coming through the doors of Dollar Tree and other discount retailers.

Traffic's already rising for Dollar Tree of late, although that's more to do with the pandemic as consumers are stockpiling day-to-day essentials. In its first-quarter results of fiscal 2020, which the retailer released n May 28, net sales of $6.3 billion were up 8.2% year over year.

But this isn't normally a high-growth stock; in its most recent fiscal year, Dollar Tree's top line grew by just 3.5%, and by 2.6% the year before that. Stability is what's great about this company -- only once in nine years has Dollar Tree incurred a loss.

Dollar Tree's stock is a cheaper buy than the other stocks on this list, trading at 3 times book value and at a price-to-sales multiple of less than 1. But its price-to-earnings multiple of 26 is still a bit rich for a company that may not generate a whole lot of revenue growth over the long haul, which is why I'm waiting for its stock to fall before buying shares. Dollar Tree's stock suffered a big decline in March when it fell to just $60 in the midst of the market crash.

Which stock is the best buy today?

Here's a quick glimpse of how the three stocks are doing this year compared with the S&P 500:

ONEM Chart

ONEM data by YCharts

Given that a crash may be imminent, the safest of the three stocks to buy today is Dollar Tree, as it's the most reasonably priced. It's a good value buy that can be a solid investment to hang on to for many years.