It turns out that Vladdy was suffering from a bum knee. Here's the link to the story. A short quote from the article (I hope this follows correct quotation guidelines):
During his lengthy slump, Guerrero didn't offer any excuses, but it was later revealed he was having trouble getting any lower-body support in his swing with a knee problem that weakened his leg drive.
"My knee wasn't feeling that good," Guerrero said. "It's feeling better now. I'm taking treatment every day. That gives me leverage -- that is the foundation of hitting. When you don't have that, you have to use your upper body. Now everything works together, upper and lower body."
Now that he is better, our offense should be 10 times better. Look out!