Vernon Wells starts the 2011 season mired in a horrible slump. His 4 for 44 with a double and two walks resulted in a number of squandered RBI opportunities for the Angels. The slump may be less what Vernon is doing wrong than what the opposing pitchers are doing right.
During the previous three seasons, Wells's wheelhouse, the area where he generated the most power sat in the middle of the plate in.
Note the vertical reference line marking the border where the bulk of Vernon's home runs begin. This season, pitchers have been very good at avoiding that area:
The majority of pitches are to the outside part of the plate avoiding Vernon's home run zone. In the past, Wells did a good job picking up doubles and singles in those areas, so his problems are more than just good pitching. As long as Vernon doesn't hit those pitches on the outside part of the plate, however, there's no reason to come back inside.