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 potash stocks PotashCorp (NYSE: POT), Mosaic (NYSE:MOS), and Intrepid Potash (NYSE:IPI) all popped about 5% today on reports that Russian billionaire investor Suleiman Kerimov may sell his 21.7% stake in Uralkali, the world's largest potash producer.

So what: Potash stocks plummeted in late July after Uralkali decided to break up its cartel with Belarus, but today's rumors -- Kerimov is seen as the main engineer of Uralkali's "volume over price" moves -- raise the possibility of a complete change in direction. One of the prospective buyers named in the story, billionaire Vladimir Evtushenkov, has denied any interest in purchasing Kerimov's stake, so Fools shouldn't get too excited over the news.

Now what: I see today's buzz as a particularly attractive catalyst for potash stocks as a whole. After all, the group has been beaten down so much that the risks -- Uralkali predicted that potash prices would sink 25% as a result of the cartel breakup -- already seem baked into their valuations even if there isn't any substance behind the rumors. So while it's not usually a good idea to buy into a stock based purely on speculative reports, the sector's downside seems limited enough to take a conservatively sized shot.