Gast was selected in the 6th round of the 2010 draft out of Florida State University. Gast has already had Tommy John surgery (in high school) and his repertoire focuses on a fastball that sits around 90mph and a curveball in the 70s. Gast caught the attention of many with a flashy pick off move showcased in a few Cardinals' spring training games. He pitched a handful of games in Batavia after being drafted. In 2011, he skipped Quad Cities and started in Palm Beach. He'd make the jump to Springfield that year, start at Sprignfield again in 2012 before moving to Memphis to finish the year.
Additon has been around for a long time after being drafted in 2006 out of high school. He's spent time at every level of the system finally working his way to AAA Memphis for a partial season in 2011. He's got a sub-90mph fastball as a starter and is reliant on command as much as pure stuff.
Arguably one of the most under the radar pitchers, he followed a similar path Gast. Drafted 3 rounds after Gast out of Oklahoma State. His fastball was a tick below Gast's at draft time but has improved since then. Lyons complements it with a changeup and a curveball.
A look at their 2011-2012 stats:
The simple take away from this chart is that Tyler Lyons has, to date, out pitched either of his counterparts. He's a better strikeout pitcher who walks fewer batters. In the two prominent areas that pitchers have more direct control over, Lyons is outpacing both Gast and Additon. What's noteworthy is that while his splits are less pronounced than Gast or Additon, he's a better pitcher overall and still comes out ahead when looking at the numbers as splits.
All three of these pitchers are questionable as starters for the long term from a scouting perspective. Their fastballs simply shouldn't install much in the way of confidence about their long term projection. That said, Lyons has outpitched his scouting report for two years now. If the Cardinals are going to look internally for left handed relief options, he may be the best choice. Even over someone like Sam Freeman.
There's room for someone like Affeldt, Burnett or Gonzalez to be more successful in the majors than either of these players but, statistically, Lyons looks like the best choice as far as internal options.