How Danny Duffy stopped worrying and learned to love his fastball in the bullpen

The moment served as an April lesson for Danny Duffy, a brief tutorial as he adjusted to a full-time role in the Royals’ bullpen.

Last Tuesday, in the late innings of a game against Detroit, Duffy threw a 2-2 slider to Tigers catcher Jarrod Saltalamacchia. The pitch touched 85 mph and caught too much plate. Saltalamacchia hammered it 425 feet to center field at Kauffman Stadium, a three-run homer that derailed manager Ned Yost’s plans to rest his top bullpen arms in an 8-6 victory.

As Duffy returned to the video room at Kauffman Stadium and inspected the footage from the at-bat, the problem was glaring. He had started Saltalamacchia — a hitter who excels against off-speed stuff — with a 97 mph fastball for a strike. He had followed by throwing a slider, change-up, slider, and finally, another slider. The final breaking ball did not fool Saltalamacchia. The lesson was apparent, Duffy said.

“When you have that kind of fastball in the tank, use it,” Duffy said. “Use it.”

In his next two appearances, the left-handed Duffy needed just 12 pitches to record scoreless innings against the Tigers and Orioles. He threw 11 fastballs during the two outings. His only off-speed pitch: A slider that procured a strikeout from Adam Jones.

In his last two appearances, Duffy has stabilized his month after he opened the season by allowing five earned runs in his first 7  1/3 innings. His ERA has dropped from 6.14 to 4.82 over the last week. Yet he is still learning to harness the potential in his fastball, which has added nearly 3 mph since heading to the bullpen last fall.

In the early weeks of the season, pitching coach Dave Eiland has delivered a simple message: If the fastball is there on a certain night, you have to learn to pitch off it.

“You don’t try to overly make them miss, but kind of let themselves miss, if that makes any sense,” Duffy said. “There’s a pretty good possibility of people getting themselves out, because my fastball has had so much life lately.”

For Eiland, the Saltalamacchia at-bat translated into an easy teaching moment.

“He threw a first-pitch fastball,” Eiland said, recalling a conversation with Duffy. “The guy cheated to get to it. He was still late, and fouled it over our dugout. And you proceeded to throw three or four offspeed pitches in a row to him. It just doesn’t make any sense. You just got to come in, and trust it, and come after them.”

As a starter for most of his career, Duffy’s fastball averaged 93.6 mph. He possessed an electric arm, but he could not afford to cut loose for six or seven innings. As a left-handed reliever unleashed in shorter bursts, his fastball is sitting at 96.1 mph and topping out as high as 98. The stuff is there to be a dominant reliever, Yost said. The issue during the season’s opening weeks centered on pitch selection.

“Against just about anybody, you really have to mix it up,” Duffy said. “But when my fastball has been as good as it has been lately, you can throw everything off of that.”

Eiland points to Duffy’s battle with Jones, the Orioles' center fielder, in his last outing. Duffy finished the at-bat by striking out Jones with a slider.

“He got two strikes on him and threw a hard, back-foot breaking ball,” Eiland said. “But he expanded the zone. When you get ahead, you can expand the zone. If you come in throwing 97, 98, they’re geared up to a certain fastball. And now you expand the zone.”

After his last two fastball-heavy outings, Duffy is now throwing his heater nearly 79 percent of the time this year, which would be a career high. He has backed off the slider, preferring to deploy it in the right counts. His usage of his change-up has remained steady. But after more than three weeks back in the bullpen, Duffy has been reminded of something simple: He is the rare reliever who can throw a baseball 98 mph from the left side. If you have that in the tank, you might as well cut loose.

“You have to know what you brought to the dance that night,” Eiland said, “and dance with it.”

This story was originally published April 26, 2016 at 1:51 PM with the headline "How Danny Duffy stopped worrying and learned to love his fastball in the bullpen."