It's a gorgeous Saturday in late February in Mesa, Arizona, and Athletics designated hitter Brent Rooker is full of joy -- partly because two days earlier, he had gotten his first hit of spring training after an 0-for-5 start. Not 0-for-50. Not 0-for-15. That's right: 0-5. He's discussing a salary cap, meteorology, dunking a basketball, X, karaoke, country music, throwing a football, his two daughters and changing diapers -- a skill which, he says, "I am good at. And I'm sure my confidence in that will never waver.'' On most other things, however, he is charmingly self-effacing. What's something you're terrible at? "Baseball,'' he answered. That's coming from a player who, over the last three MLB seasons, has hit 99 homers, competed in the Home Run Derby and made two All-Star teams. "I'm not great at baseball most of the time,'' Rooker said. "And I let myself know it. My teammates will tell you that's my way of coping. Negative self-talk.…