Inside the Phillies: Nola's curveball, while mistaken for a slider, is a weapon

In the last 15 months, countless hitters at four levels of pro baseball have found themselves quickly behind in counts because of Aaron Nola's pinpoint fastball command. Then will often come his best secondary pitch, a breaking ball, and with it an obvious question from those watching.

"Was that a slider or a curveball?"

Since the Phillies drafted Nola seventh overall in the 2014 draft out of Louisiana State, his breaking pitch has been labeled as both in articles and in interviews with opposing hitters. Earlier this season, when Nola pitched for double-A Reading, Zach Eflin would chart pitches in the seats behind home plate and hear fans asking the same question. He relayed it to his rotation mate later on, if for no other reason than to rattle his cage.

"C'mon, man," Nola would say with a laugh, "it's a curveball."

Nola is adamant about that, although he understands his three-quarter arm slot can sometimes make his breaking ball appear more like a slider. Whatever you want to call it, the pitch has proven a weapon for the rookie righthander, who through nine starts looks the part of a mainstay in the Phillies rotation for years to come.

Thirty of Nola's 44 strikeouts have come on his curveball, against which opponents are hitting just .175, according to FanGraphs.com. He has allowed only three extra-base hits off the pitch, each occurring over his last two starts. Two came in Wednesday's loss to the New York Mets - the worst outing of his young big-league career - on plays that should have been outs or, in the case of Ruben Tejada's inside-the-park home run, at worst a single.

Nola throws his curveball for strikes 67.2 percent of the time, the highest rate of the 22-year-old's three pitches, according to FanGraphs.com. He uses it against righthanded and lefthanded batters and can typically locate it where he wants. The pitch - which ranges from 74 to 79 m.p.h. - has helped him induce early outs in addition to strikeouts. He has not issued a walk with it in 532/3 innings.

"I'm pretty confident in it," he said this past week. "I feel like I can throw it any time in any count and for the most part put it where I want to. It's really helped me go through games pretty well."

There is of course room for more consistency with both of his secondary pitches - a change-up is the third pitch in his repertoire - but he has made strides with his curveball this season. He used his three-plus months in the minor leagues fine-tuning the mechanics of the pitch, spending more time on it than usual in his bullpen sessions and while playing catch. He became more consistent with his grip and made sure to "try to just throw it out in front of me instead of trying to make it do too much," he said.

The extra work resulted in a sharper breaking ball with added depth. By mid-June, when he was promoted to triple-A Lehigh Valley, he felt he had turned a corner. Among the major-leaguers who have fallen victim to the pitch since his July 21 big-league debut are Troy Tulowitzki; Edwin Encarnacion; Jose Bautista; Evan Longoria; Kris Bryant (twice); and Anthony Rizzo, who whiffed on a curveball that hit the Chicago Cubs first baseman's back leg after his swing.

Said catcher Cameron Rupp, "He throws it for strikes. He starts it in the zone, and he starts it out of the zone. He can backdoor it. He can put it wherever he wants, pretty much."

"It's a great pitch," said Eflin, one of the Phillies' top pitching prospects, who recently added a curveball of his own. "It's a huge weapon that he has."

When Nola was in Reading earlier in the season, Eflin would tease his him by calling the pitch a slider.

"It was more of a joke that I played, when it would be more like a [1 o'clock to 7 o'clock tilt] than it was 12-6," Eflin said. "Sometimes, when I would catch [him] I would call it a slider, and he would get all pissed off."

Phillies interim manager Pete Mackanin recently described Nola's curveball as "a hybrid." Adam Morgan, the rookie lefthander who debuted a month before Nola, initially thought it was a slider before Nola told him differently. "I feel like it's a slurve," Morgan said.

Nope.

"At the end of the day," Nola said, "it's a curveball."

@jakemkaplan

Matt Breen contributed to this article