Diamondbacks pitching coach: Wade Miley 'hasn't reached his full potential yet'

Diamondbacks pitching Mike Harkey recently opined that left-hander Wade Miley, who was traded to the Boston Red Sox last month, has the ability to elevate his game to a level he didn't reach in his four-year stint with Arizona.

"He definitely hasn't reached his full potential yet," Harkey told Brian MacPherson of the Providence Journal.

Miley's tenure with the Diamondbacks began auspiciously, as the former first-round pick fashioned a 3.33 ERA and an impressive 3.89 strikeout-to-walk ratio over 194 2/3 innings in 2012, finishing second in Rookie of the Year voting.

Command issues began to surface in 2013, however, as his walk rate jumped more than three percent and his ERA increased to 3.55 (109 ERA+) over 33 starts.

The problems worsened in 2014, when he authored a career-worst 4.34 ERA with a 1.40 WHIP and 8.7 percent walk rate, but Harkey suggested improved command of his fastball could make Miley one of the game's top left-handers.

"I truly believe that once his fastball command gets where he's capable of getting to, he's going to be a guy like a Jon Lester," Harkey said. “One of the things Jon Lester possesses is the ability to put his fastball where he wants to in key situations, and that’s what makes him so good in big games. 

"Wade is right on the verge of that, of being that guy who can consistently repeat his delivery and make pitches with his fastball."

Miley, who was shipped to Boston in exchange for Allen Webster, Rubby De La Rosa and Raymel Flores, will be counted on to provide a high volume of quality innings next season for a rotation lacking in premium talent. 

Despite his struggles last season, Miley's strikeout rate elevated considerably and he continued to induce ground balls with impressive regularity.