The table below focuses on the lefthanded pitchers with the Top 10 ERAs in baseball and compares them by average fastball velocity, and movement, both in the horizontal and vertical directions. All data again from the fangraphs website.
In case tables aren't your style: compared to the lefties with the top ten ERAs in baseball, Niese's fastball has above average horizontal movement and below average vertical movement. In both cases, his difference from average is less than one standard deviation, so we can, by way of shorthand, and given the small samples sizes from Jon Niese, suggest that his fastball has average movement compared to this successful group. Standard deviations measure the amount of variance in a data set. (Last two sentences added/edited for clarity.)
By the way, I'm open to the argument that ERA is hardly the best or only way to judge pitchers. A more general list of the top lefties in the game would probably have to include Sabathia and Kershaw, but I wanted something clean and empirically based, so ERA worked fine for my purposes here. VORP doesn't sort by handedness as far as I can tell, for example.
Note also that the average fastball velocities listed under the pitchfx pages under the fangraphs website differ slightly for the velocity values listed under the "Pitch Type" table under the each player's "Season Stats" page, which I used to derive the original velocity table in the first post. I have not altered the original velocity values, although they tend lower in pitchfx, supporting the argument that Niese's heater compares just fine with those lefties who have had the most success over the first half of the 2009 MLB season.
Again, the takehome message:
There's simply nothing in this data to suggest that Niese's fastball is too straight relative to baseball's other successful lefthanders. The key again, is not pitch movement, as much as it is pitch location.