To me, the concept of lineup protection is that it enables certain hitters in a batting order to receive better pitches to put in play. The dangerous teams out there possess the circular lineups, like the Yankees.
But if a quality hitter in the 3 spot doesn't have a dangerous clean-up hitter batting behind him, pitchers would be more liable to throw more junk. As a pitcher you wouldn't want to put a hitter on base with a walk, knowing that the cleanup hitter is batting next and poses a real threat to get 1 or 2 RBI's.(or knowing a dangerous #5 hitter is up next, too.)
Just my .2
No, I hear you, and that's the popular notion of it. Better pitches means basically more fastballs, for the reasons you stated.
But there's been guys who actually look at every single pitch to see if it's true. They also look at lineup construction to see if there's any outliers that result for batters when they have different players behind/in front of them. After looking at these results, they see that there's not much difference. Great players, like Adrian Gonzalez, will hit well with a shitty team like SD, or with better hitters around him like Youkilis. At the end of the day they'll still get their numbers. Could this make a difference in a few at bats? Of course. But it normalizes over time and genuinely won't skew a player's stats significantly.
Markakis was a great hitter in 2008 and I think he had Aubrey Huff as his clean up. He's a great hitter who's had two or so "off" years. I think we're just going to see him gravitate back to the player he is, rather than giving Guerrero and company credit for it.
There's a lot of stuff out there that discusses this stuff. If you're interested, here's an article that probably says it better than I could:
http://www.baseballprospectus.com/unfiltered/?p=1042But you can probably find articles that argue the contrary. To me, these guys have made sense most of the time.
