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: Momenta Pharmaceuticals (Nasdaq: MNTA) shares fell 10% in trading early Tuesday after Teva Pharmaceutical Industries (Nasdaq: TEVA) said it expects FDA approval this year on a drug to compete with Momenta's enoxaparin.

So what: A day after Momenta announced earnings of $0.70 a share, which beat estimates of $0.52 a share, Teva decided to rain on Momenta's parade. Teva management said it would be "deeply disappointed if we didn't get the approval this year" only a day after Momenta's management touted its solid position as the only generic version of Lovenox.

Now what: Teva did not announce a timeline for FDA approval, but the end of the year is fast approaching and Momenta won't be able to enjoy its lone generic status for long the way things are looking. Increased competition in generics may also put pressure on sanofi-aventis (NYSE: SNY) to lower the price of Lovenox to compete on cost. All in all, it's bad news for Momenta, and I don't see today's move as a great buying opportunity given impending competition.

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Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

Momenta Pharmaceuticals is a Motley Fool Rule Breakers pick. The Fool owns shares of Teva Pharmaceutical Industries. Try any of our Foolish newsletter services free for 30 days. 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 has a disclosure policy.