Salvador Perez underwent knee surgery, and now is expected to miss half of the season:

In other words, there’s a strong chance the 21-year-old catcher will miss the entire first half of the season, which is an awfully tough break so soon after signing a long-term contract extension that could potentially keep him in Kansas City through 2019.

Long term, this isn’t a big deal, but it does make the Royals a little less likely to compete in 2012.