"He's going to be great, right?"

When Brett Lawrie was called up last season at 21, his 171 plate appearances in 43 games confirmed a lot of assumptions about him as a player. He's gritty and aggressive, can cover the whole plate, and has quick bat speed. The small sample also suggested that he had power and plate discipline, his .293/.373/.580 (.953 OPS), and nine home runs, putting him in the company of other great young players like Al Kaline (.967 OPS at age 20) and Jimmie Foxx (.964 OPS at age 20).

"He'll keep it up next season, won't he?"

Such a monster debut set a high bar for a repeat performance, and in 2012 Lawrie failed to clear it, hitting .273/.324/.405. He matured at the plate in some ways, but devolved in others - he struck out less, but also walked less and argued with umpires more. The biggest difference was a drop in power. His 2011 isolated power of .287 fell to .132 in 2012. He hit nine home runs in his abbreviated rookie season, but hit just two more (11 total) in 2012, despite 365 more plate appearances.

"But...why? Where did his power go?"

That's a question that's usually difficult to answer because the reasons are unique to each player. Some lose power because of injury, or because pitchers finally learn their weaknesses, and sometimes it's just bad luck. In Lawrie's case, it's a little easier to assess what's happened to his power: There has been expected regression, but his approach at the plate has also changed, resulting in a lot of ground balls.