Yes, as established pitchers often get the borderline calls, the inverse is also true. An unproven starter isn't going to get as many calls when he's pitching to a big-time hitter. I don't think that should be the case, but it is what it is. When Joe Mauer takes a close pitch he's more likely to get the ball call than Drew Butera. If the umpire doesn't have a great look at the pitch he might defer to a hitter that he thinks has a good eye. Come to think of it, that may be an interesting research project. What % of borderline pitches go the way of the hitter when the batter is Derek Jeter, for example, as opposed to Trevor Plouffe?