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: Finisar (Nasdaq: FNSR) popped 10% in intraday trading today after an analyst upgraded the stock.

So what: Citi Investment Research upgraded the stock from hold to buy, and raised its price target to $24 from $16.50. The analyst explained that he sees an opportunity for the stock's growth, expectations are "fully reset," and the stock has a "rational" valuation.

Now what: Finisar stock fell from more than $43 at the end of February to $18.67 at yesterday's close, thanks to an earnings miss and disappointing outlook in March, followed by a disappointing update to guidance in June. What's more, my Foolish colleague Seth Jayson recently noted that Finisar's earnings aren't so hot. With EPS expected to fall 40% in the coming year, and a forward P/E ratio of 20.7 times, it seems hard to justify the current price unless earnings expectations are far too low.

Interested in more info on FNSR? Add it to your watchlist by clicking here.

Fool contributor Cindy Johnson does not own shares of any company named above. 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.