Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: MasTec, Inc. (NYSE: MTZ) stock was down as much as 18% at one point this afternoon, before rebounding slightly. Currently (just after 3 p.m. EDT) the stock is still down about 11%. 

So what: MasTec filed a news release late yesterday afternoon, announcing that it would not release its 10-K annual report on that date. This is the second delay in the filing of the company's annual report. On the quarterly earnings call on Feb. 27, VP of Investor Relations Marc Lewis said:

As we announced in our press release last night, The Audit Committee of the company's board of directors, with the assistance of independent counsel, is undertaking an independent review primarily to determine if certain cost to complete estimates, currently believed to be in the range of zero to $13 million, which were recognized during the company's third quarter of 2014 should have been recognized during the second quarter of 2014. The company currently believes that the review will not negatively impact its full fiscal year 2014 results. Because the Audit Committee's independent review has not yet been completed, and no complete conclusions have been established, the company expects to extend until March 17, 2015 the filing date of its Annual Report on Form 10-K for the year just ended, as permitted by SEC rules. 

Here we are, three weeks later, and the company is further delaying the annual report. Mr. Market is clearly spooked by this. Since the earnings call, the stock has fallen more than 20% including today's big drop.

Now what: The market hates uncertainty, and frankly MasTec has created some of that with another delay in releasing the annual report. However, it's worth noting that the investigation that's delaying the release -- at least what we were told -- isn't expected to impact the company's results. It's supposedly about which quarter during the year the company was supposed to recognize certain costs. 

I'd guess that the lack of new information is what's spooking the market, and not any material "bad news." If you're a believer in MasTec's long-term prospects, this could be a good opportunity to pick up some shares.