Carlos Peguero of the Seattle Mariners isn't hitting for a high average or getting on base much, but he is smacking the ball. He slugs .457 with a .223 batting average, indicating that his average hit is better than a double.
Rookie batters are known for their ability to hit the fastball, but they need to learn to hit major league breaking pitches. Minor league pitchers can throw hard, but what often keeps them in the minors is their inability to fool batters with off-speed pitches. When young hitters reach the majors, they have not see very many good breaking balls and change ups.
Peguero exhibits the exact opposite tendency.
That's about as cold a strike zone as you'll see. In 38 plate appearances ending in a fastball, Peguero owns a .176/.263/.176 slash line, good for a .219 wOBA. Lower the speed, however, and the zone lights up:
In 39 PA against these pitches, Carlos posts a .324/.359/.811 slash line with eight of his 12 hits going for extra bases and a .474 wOBA. Until Carlos catches up to the fastball, there's no reason not to challenge him.