There is significant worry that the recent decline in copper and China's economic woes might be the start of a wider correction. There are certainly some concerns reflected in the market internals: fewer new highs overall, and no components having hit new highs.
Still, it's hard to see imminent signs of a significant market drop. The advance/decline line is still near a new high, and that usually turns down well in advance of a significant market correction.
I would also note that financials have been market leaders recently, with the main at a new high on Monday. They usually turn down early as well.
Some say that if you can't take the whole market down, try and slow down the 'Big Momentum' names. Much was made overnight that certain sectors are too "frothy"; bears were gloating overnight over the big declines yesterday in fuel cell stocks like PLUG and FuelCell.
The lines of attack from bears are fairly easy to see: the obvious "Big Mo" targets include medical/biotech. Indeed, there are some big gains in that sector this year. Here are just a few (percentage change):
Illumina 50 percent
Alexion 32 percent
Actavis 25 percent
Biogen Idec 20 percent
Regeneron 19 percent
Still, these companies are much better financed, and generally have stronger drugs (even if there are only or two per company) than in the last major shakeup from 2000 to 2002. Another obvious choice is anything in the vague "cloud computing" space, which has also seen good gains:
F5 Networks 23 percent
Workday 21 percent
Vmware 15 percent
Cvent 15 percent
Salesforce.com 10 percent
Big Data is another obvious choice: Tableau Software (DATA) and Splunk (SPKK) for example are up 32 percent and 23 percent respectively this year. But none of these sectors have cracked yet.
Elsewhere
1) One initial public offering (IPO) has been postponed. Diamond Shipping, a deep sea bulk transport company, has reportedly put off its flotation scheduled for today at the NYSE. It's largest shareholder, Wilbur Ross, implied the price was too low.
How low? No one said, but the company was offering 14 million shares at $14 to $16, and IPO traders told me the book was below $10 a share. Ouch. I would not extrapolate much about this for the rest of the IPO market, however. New issues are a sector play: shipping is not a hot sector play.
2) Surprise! Another retailer guides lower (it's a broken record by now). Express reported earnings and revenues below expectations and guided 2014 share price to $1.03-$1.23, well below consensus of $1.58.
Says CEO Michael Weiss: "The start of 2014 has nevertheless been extremely difficult, with traffic down significantly, negative comparable sales and the promotional environment remaining intense." He concludes by saying that "a material uptick in traffic is not necessarily imminent" and that "the promotional environment will continue."
3) There is a little more pressure for the market leaders. Small- and mid-cap stocks are the market leaders this year, but this week they have been notable under performers, particularly yesterday.
The MidCap Index is down 1.4 percent, the small-cap Russelll 2000 down 1.4 percent, while the S&P 500 is down 0.5 percent. For the year, the Russell 2000 and S&P Midcap up 2.0 and 2.3 percent respectively, outperforming the 1.0 percent gain of the S&P 500.
Asia saw a rough session, with the Nikkei ending down 2.6 percent (now down 9 percent for the year); elsewhere, Hong Kong, Korea, and Singapore were also down more than one percent. Most of Europe also down more than one percent.
—By CNBC's Bob Pisani