The pitchers we're looking at here aren't necessarily the game's best, and their key pitches aren't necessarily the best of their type. These are pitchers with upside who -- with a tweak or two -- could markedly improve their performances this season. But they each have a "problem" pitch that could prevent them from reaching their upside, including one with a pitch he is so totally reliant upon that it needs to be supplemented for him to thrive or survive long-term.
I'll be referring to contact scores throughout this article, which is the relative production allowed by a pitcher overall or on a given pitch -- 100 equals the league average, and a figure less than 100 is better than league average; more than 100 is worse. Unadjusted contact score reflects the actual results allowed, while the more useful adjusted contact score reflects how a pitcher should have performed based on their individual batted-ball exit speed/launch angle mix.
Chris Archer, Tampa Bay Rays: Four-seam fastball. Two of the pitchers on our "problem pitch" list tied for the AL strikeout rate lead among ERA qualifiers, at 27.4 percent. Archer is a three-pitch guy whose overall swing-and-miss rate of 12.2 percent was significantly above league average. That success was driven by a 19.0 percent whiff rate on his slider.
Archer had a difficult time managing contact, however, and most of the damage was done against his four-seamer. His whiff rate on that pitch was a lowly 6.2 percent, well below league average, yet he depended heavily on that pitch, throwing it 47.5 percent of the time. Hitters raked against it, hitting .349 and slugging .660, with the most damage done on four-seamers they hit into the air (153 adjusted contact score).