Mechanical flaw responsible for Span's 2010 offensive woes?

There have been a lot of theories thrown around this off-season attempting to identify the reasons behind Denard Span’s 2010 regression: He’s been hitting with two-strikes more frequently. The transition to natural grass from turf has shaved points off his batting average. He played too much and needed more rest. While all of those were factors to some extent, more tangibly, Twins Hitting Coach Joe Vavra recently acknowledged a slight flaw in his mechanics last year that he believed contributed to his offensive woes. In conversations with Vavra on the subject of Span, 1500ESPN’s Phil Mackey wrote that Vavra attributed the increase in grounders on the center fielder not keeping his head as still as he had in previous season: "A little bit of a mechanical thing. He was raising up off the ball when the ball was coming in. Usually the head's really still, and with him he was raising up a little bit. So when he went to swing it, he wasn't seeing actually wh...