PEORIA, Ariz. — Dinelson Lamet is in need of a change. Or, maybe he isn’t.



The Padres right-hander threw his fastball 55.2 percent of the time as a rookie last season, according to Statcast data. He threw his slider 38.9 percent of the time. Unsurprisingly, both pitches rate as plus. Changeups, meanwhile, accounted for just 5.2 percent of Lamet’s deliveries.



Few starters were more reliant on two pitches in 2017, and Lamet posted a 4.57 ERA indicative of the predictability of his approach. However, he also struck out 10.9 batters per nine innings, ninth-best among starters who recorded at least 100 innings. In major league history, only four rookie starters, all of some repute—Kerry Wood, Dwight Gooden, Mark Prior and Hideo Nomo—cleared 100 innings with a higher punchout rate.



At the end of last season, Lamet identified the development of a third pitch as a critical objective. He had devastated numerous opponents, limiting...