For today’s leadoff hitters, on-base percentage is king. That’s why, when Rafael Furcal opted for Tommy John elbow surgery and John Jay had a slow start to the season, the Cardinals decided to give Matt Carpenter a shot at the top of the lineup, even though he had never hit in that spot before. In four years in the Minors, Carpenter had a .408 on-base percentage and a reputation for grinding out lengthy at-bats.