It's make-or-break time for the first-quarter earnings season, and it comes just as the stock market is showing signs of strain.
About 170 S&P 500 and 10 Dow companies report earnings in the week ahead, and they include everything from tech icon Apple to industrial names like Caterpillar and energy companies like giant Exxon. As of Friday, a fifth of the S&P 500 had reported, and two-thirds had better-than-expected earnings. But an unusually high amount—57 percent—missed their top-line revenue estimates, according to Thomson Reuters.
That's a cause for concern, since stocks traded in one of the most volatile seesaw patterns of the year in the past week, as worries about global growth increased amid a dramatic sell-off in commodities. The Dow finished its worst week this year 2.1 percent lower at 14,547, and the S&P 500 was down 2.1 percent at 1,555. The Nasdaq was down 2.7 percent for the week, even with Friday's big gain of 1.3 percent on the back of a tech rally.
The week ahead also has a light but important economic calendar, including home sales data Monday and Tuesday, durable goods Wednesday, and the first look at first-quarter GDP Friday. Even though it is a reading of past activity, first-quarter GDP is important since, at estimated 3 percent growth, the rate is about double what is expected for the current quarter. Traders have also been fixated on events surrounding the Boston Marathon bombers, though it was not seen as a market factor.
"I think this rally is a little weary," said Art Cashin, director of floor operations at UBS. "The 'buy the dips' have been in and they bought most of the dips. The question is will they continue, or is the market getting ready for the spring swoon everyone is talking about."
Cashin said the Dow broke an important trend line at 14,500 Friday as IBM had its worst day in eight years, but it rose back above that level by the end of the day. The S&P struggled at its 50-day moving average Thursday, but it too got about a dozen points above it by Friday afternoon. Commodities markets were calmer by the end of the week, but gold lost 7 percent in the past week, sliver lost 12.8 percent, copper lost 6 percent and oil lost 3.6 percent.
(Read More: IBM's Ominous Sign to the Stock Market)
"By any sort of measure, we're kind of overdue for some sort of a pullback, and maybe we're finally going to get it," said Bill Stone, chief investment strategist at PNC Wealth Management. Year to date, the S&P is up 9 percent and has not had a significant pullback. He noted that the economic data has been disappointing.
"Once you had a market that moved up like this one has, expectations are really your enemy. We're not meeting expectations … then you throw in earnings season. Earnings, I would argue, are coming in better than expected. Underneath the surface is something that's not quite so healthy," he said. "They're struggling on the top line, the revenue side. That's indicative of a global economy growing below trend."
The commodities sell-off is also signaling a global weakening, and it accelerated when China released disappointing GDP data Monday.
(Read More: Copper Falls Below Key Level; Warning Signs Flash)
Gina Martin Adams, institutional equity strategist at Wells Fargo Securities, has also been expecting a pullback. "I still think we're in some sort of process of trading a top. It's hard for me to say," she said. "There has been enough disturbance to suggest the trend is now in question, which is the first time you can say that this year. Certainly the factors have been lining up."
"Every April we have this. It's scary how the market is trending exactly as it has for the last four years running," she said. "There is this confluence of factors. The fundamental case—everyone was excited about the economy improving, but that story broke down. The earnings are not improving. The commodities complex looks just like last year."
Even though economists expect a weaker economy, they do not expect it to be as soft as last year, and stock strategists also expect the market to rebound later in the year, after any sell-off.
Adams said seasonally, April can actually be a good month for stocks so they may hold on, but in the next few weeks, there could be a downdraft as there was in the past three years. "May is when you get a little worried … we've got a sideways trend in place," she said, adding it's also possible there could be a sideways correction. That means stocks would grind in within a range, instead of selling off.
This makes the earnings season particularly key, as traders look for clues about the extent of the soft spot and its impact on corporate profits.
"The next two weeks are really important. That's when the bulk of the market cap reports. They will be extremely important. There's a limited amount of economic data to consume. The huge reports come at the beginning of the month," when April employment data is released, Adams said.
She added that is especially watching industrials and technology. "Those are the areas where the market is expecting the greatest weakness. If there are areas where there could be a surprise and guide higher, those could be the areas. They should be the areas where the turnaround story could occur, should it show up. I'd like to see that, but it's not in my forecast."
Industrial companies GE and Honeywell both reported earnings that slightly beat expectations Friday. GE, however, reduced its forward guidance while Honeywell slightly raised it. In tech, the message has been mixed. IBM fell 8 percent Friday after its weak earnings report, but shares of Google and Microsoft both gained even though revenues missed slightly.
(Read More: What to Make of Google's Earnings: Pro)