Disclaimer: Nobody who watched Albert Pujols play for the St. Louis Cardinals last year expected him to hit .208/.255/.292 through his first month in a Los Angeles Angels uniform. (Maybe hoped, but never expected.) That said, there were warning signs there for people who, spooked by his relatively human 2011, trawled FanGraphs for answers.
For instance: Last year his O-Swing%, the percentage of pitches a batter swings at outside the strike zone, increased from 21.7% in his career to 31.8%, after a slow decrease over the years; this year's it's an incredible 40.1%. Of course, he's also making a lot of contact with them—81.5% of the time—which might explain some of the weak contact.
That erosion of plate discipline was the biggest concern for Albert Pujols fans who expected the Cardinals to sign him to a billion-dollar contract in the offseason; now it's an I-told-you-so. On a less vindictive front, Viva El Birdos commenter and professional swing coach thepainguy thinks the problem might involve his back leg.