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: Office product supplier Avery Dennison (NYSE: AVY) saw its shares sink 13% today after it disappointed investors with its second-quarter outlook.

So what: This wasn't Avery's full earnings release, but it was like a warning punch in the gut for investors. Instead of earnings per share being somewhere around $0.88 like analysts expected, Avery is seeing more like $0.74 to $0.79 in the crystal ball.

Now what: An earnings miss can be understandable if there's a big charge in a quarter, but revenue will also fall well below estimates, so this is the worst kind of earnings miss. Avery said sales would be about $1.7 billion, which is $130 million below what analysts expected. I don't see any positive way to spin this today and would stay far away from Avery going into earnings season.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.