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 minor-league investment bank Greenhill (NYSE: GHL) went decidedly downhill today, falling as much as 14.1% on more than seven times the average trading volume.

So what: According to a Bloomberg report, superstar merger specialist Tim George is leaving Greenhill for rival Lazard (NYSE: LAZ). He's the third managing director to leave Greenhill since early June, a steep climb from the traditional rate of about one such senior executive leaving per year.

Now what: Greenhill still has 26 managing directors on payroll including six in the New York office that George left behind. Still, he was involved in some of the largest deals Greenhill has managed in recent years, including the sale of Applebee's to IHOP (now collectively known as DineEquity (NYSE: DIN)). A talent of that caliber isn't easily replaced, especially when he's joining a direct competitor. Greenhill just lost a small but valuable weapon in its arsenal for battling larger and richer rivals such as Jefferies (NYSE: JEF) and Blackstone (NYSE: BX). The company reports earnings on Monday; look for a discussion of the George situation there.

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

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.