With the injury to Jake Westbrook, the Cardinals brought up John Gast to make a start for the big league team, and over 6 innings he performed reasonably well, with 3 strikeouts and a walk, earning another start in the big leagues. Gast was picked in the 6th round out of college by the Cardinals, and was their 13th best prospect (according to Baseball America) by the end of the year (he had slipped to number 26 by 2012). This was his first Pitch F/X game, so let's look at Gast and see if he is someone who can stick in the big leagues long term as a starter.
First let's look at his release point in graph form:
Here is where Gast was throwing the ball, his strike zone with the official results of each pitch:
Here is what his stuff looks like via his spin and speed chart:
47 Fastballs: 88.38 MPH, Dallas Braden
3 Cutters: 83.12 MPH, Bruce Chen
5 Curves: 73.46 MPH, James Russell
16 Changeups: 79.4 MPH, Mark Buerhle
As a prospect, Gast was known for his changeup, as it ranked the best in the system after 2011. Braden's cutter was also very close to Gast's in velocity, but Braden's curve is harder and his change much softer. Jason Vargas also hovered close on some of the pitches, which would make some sense, as Vargas is a cutter and changeup heavy pitcher.
So the stuff is obviously below average, but you have to like where his pitch comparisons look like, as he compares to some other successful soft-tossing lefties.
These are the average locations of each one of his pitches, basically where each pitch is usually going to end up:
He goes glove side with his fastball and his cutter, and arm side with his change, throwing his curveball straight down. This is the again what you might call the Jason Vargas approach, throwing fastballs and cutters into righties, trying to jam them even with bad velocity (which is a big reason Vargas is so homer prone, as many get left over the plate at 86-88 MPH), and then throwing the changeup away from them.
The problem with determining whether or not Gast will be a successful starter or not is that we still haven't really seen why some of the well below average fastball lefties are successful and some are not. If it really is the curveball/changeup usage distinction, then we would not expect Gast to be successful. I just don't know how much I buy into that distinction.