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 one-cup-coffee king Green Mountain Coffee Roasters (Nasdaq: GMCR) were leaving investors with a bitter taste as they sold off as much as 17% in intraday trading.

So what: When Green Mountain started selling Starbucks (Nasdaq: SBUX) -brand pods for its single-serve coffee brewer, investors let out a sigh of relief, assuming that it meant that Starbucks wouldn't end up being a key competitor of Green Mountain. Fast-forward to today: Starbucks has announced the Verismo, a for-the-home, single-serving coffee maker. If the Verismo puts the $39 billion Starbucks in direct competition with the $8 billion Green Mountain, there should be little surprise that Green Mountain's shares are selling off today.

Now what: The big question, then, is whether the Verismo does in fact put the two companies in a head-to-head rivalry. Starbucks and Green Mountain are doing their best to convince us it doesn't: They emphasize that the Verismo is focused on espresso and specialty drinks as opposed to good old-fashioned coffee. My fellow Fool Jason Moser shares that view, seeing the Verismo as more of an attack on Nestle and its Nespresso machines.

At the same time, it's not much of a leap to see Starbucks entering the home-brew market with the Verismo and later augmenting it with a single-cup brewer that would more directly compete with Green Mountain's Keurig.

My take is that today's announcement doesn't train Starbucks' considerable firepower on Green Mountain. However, if I were considering an investment in Green Mountain, I certainly wouldn't discount the potential for its upward climb to get much steeper.

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