Astros' Francis Martes: Developing changeup with help from Oswalt

Martes has changed the grip of his changeup from a two-seam to a four-seam grip, Jake Kaplan of the Houston Chronicle reports.

Martes impressed several hitters during his first live batting practice of the spring Friday, using his mid-90s fastball, power slider and a still-developing changeup. The 21-year-old right-hander has been receiving tutoring from former Astros ace Roy Oswalt, who spent time this week working on Martes' changeup, a pitch Oswalt believes is pivotal to the prospect's development. Martes had been throwing a two-seam changeup despite not throwing a two-seam fastball. Oswalt suggested the four-seam changeup to better deceive hitters.