I have to be honest, when I wrote the title of the post I mistakenly wrote "Wallace and Gromit."
Anyhow, in this article, we find that a checklist of things for Wallace and Johnson to work on has been passed on to manager Tony DeFrancesco (Mills expects both to be back for September call-ups). What could those things be?
For Wallace, that list probably includes identifying breaking balls (/snicker). FanGraphs says that he has a -5.5 wCB (Runs above average when seeing a curveball), a -3.6 wCH (changeup), and -1.0 wSF (splitty). He's also swinging at 31.8% of pitches outside the strike zone. And if Tony DeFrancesco sits him against LHPs, I'm going to burn down an orphanage.
For Johnson, he's going to have to prove that he won't just swing at everything. In 2009, his K% at Triple-A was 21.8% - which turned out to be fairly accurate for his last two years (it dropped to 14.1% in his short stint at AAA in 2010). In 2010, his MLB K% was 25.1% and was 24% at the time of his demotion. The only pitch type Johnson has a positive value against (again, according to FanGraphs) is the split-fingered fastball (1.1). He's getting killed on curves (-5.0) and sliders (-3.1), and even four-seam fastballs (-4.3). He's swinging at 42% of pitches outside the strike zone, and is seeing a first-pitch strike 63.8% of the time, with 12.1% swinging strikes.
Johnson is just going to have to work on his pitch selection. And his defense. Definitely his defense.