AUTiger7222
Called Up to the Major Leagues
Sample size I think plays the biggest part. Using Heyward he only has 138 PA at leadoff.
I do think there are some lineup spots that favor certain hitters. For example I'd rather have a patient hitter hitting 8th than an impatient hitter. McLouth did really well for us that 1 year hitting 8th because he took pitches and walked a ton. TLS for example may be insane out of the 8 hole. His eye would likely lead to tons of walks. Aside from that, most other hitters do better/worse in decent samples in certain spots has to do with a mental thing, Hitting is largely mental.
Bobby Cox once put Casey Kotchman in the 8th spot because of his keen eye and ability to walk and clear the pitcher. But you are right in that mental approve plays a key role as well as why some hitters do better in certain spots.