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: Shares of Exterran Holdings (NYSE: EXH) dropped as far as 21.3% on very heavy volume.

So what: This morning's second-quarter report failed to impress the Street thanks to a disappointingly large net loss in spite of great sales. Making matters worse, CEO Ernie Danner decided to announce his departure from Exterran and sister company Exterran Partners (Nasdaq: EXLP). And of course, all of this took place on a terrible market day in general, and particularly so in Exterran's oil and gas sector.

Now what: In Danner's defense, he's taking the high road by stepping out after disappointing his investors for a number of quarters. The board is now looking for a suitable replacement, and Danner keeps a hand on the rudder until they find one. In spite of the man's misgivings, Exterran Holdings sports a perfect five-star CAPS rating, just like sector peers Global Industries (Nasdaq: GLBL) and Complete Production Services (NYSE: CPX) -- maybe Ernie could be convinced to stay after all?

Interested in more info on Exterran Holdings? Add it to your watchlist.