Snakebit.

Yesterday, Dustin Pedroia managed to break the navicular bone in his left foot by fouling a ball off of it. The navicular bone (red arrow) is a disc-like bone of the midfoot; it can easily be felt on your own foot--the bony protuberance, slightly off-center of the top of the arch (toward the heel) is the tuberostiy of the navicular.

As was evidenced by the way Pedroia hobbled down the line, the navicular is essential for a normal gait. Along with the three inner metatarsals (longer bones), the three cuniforms (the small, roundish bones--I redrew two of them), and the calcaneus (the heel bone) it forms the arch of the foot. People are heavy and the purpose of the arch is to redistribute some of that weight. The bone also helps to absorb impact on heel strike and propel the body forward while walking.

The two weeks Pedroia thinks that he's going to be out seems highly optimistic; you're more likely looking at the typical six to eight weeks it takes for a bone to re-knit. But if there's any person who could look at his foot and say "Alright, bones. You are going to heal today." and have them listen to him, Dustin Pedroia might be that person.

And then today, Clay Buchholz hyper-extended his knee while running the bases. A hyper-extension occurs when a joint is forced beyond full extension and, in effect, bends the wrong way. Knees are delicate things and you'd be concerned with ligament damage but since he walked off the field under his own power, he's likely okay.