Where a player hits in the lineup matters. For every spot a player moves down the order (lead off to second, fifth to sixth, etc.), that player loses approximately 0.1 plate appearances per game, or about 16 plate appearances over the course of the season.
If a player moves from second to third… not a big change in a player’s value. But if you were originally projecting a player to bat 9th and he gets bumped up to be the lead off hitter, that could increase a player’s value 15-20% (8 lineup spots * 16 plate appearances = 128 additional PAs)!!!
I Stumbled Upon This Very Helpful Page at BaseBall-Reference.Com
Each team at baseball-reference.com has a batting order page that displays the starting lineup for each game. 
This is a great way to keep an eye on trends in a team’s lineups and to monitor where your players are hitting. I’ll often try to check this and it usually takes several clicks to drill down into a player’s game log, click on the last few games, scroll down to the box scores, click back a few times to check the next game, etc.
But these team pages will make it much easier to get the information.
