TRENTON, N.J. - Steven Matz tugged at the left sleeve of his blue Binghamton Mets T-shirt as he spoke. He momentarily looked away.

Those who know Matz from his days at Ward Melville High School and as one of the Mets' top pitching prospects say such nonverbal cues are expected when the topic of conversation is his success.

That's why what Matz said next was both surprising and significant. He shared a specific recent triumph, which meant it likely was something that made the lefthander extremely proud.

"You know,'' said a beaming Matz, his eyes sparkling, "I got a couple of big strikeouts on my curveball yesterday.''

Matz was referring to his sixth Double-A start, July 23 against the Portland Sea Dogs. With the bases loaded and one out in the fourth inning, he struck out the next two batters.

The fact that he escaped that jam wasn't all that significant. The 72nd overall pick in 2009 has been doing that for years. What was important was the way he pitched out of it: Both batters swung and missed badly at his huge dropping curveball.

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Help from Viola

It's the pitch that Frank Viola, Matz's pitching coach at Class A Savannah, and Ron Romanick, the Mets' minor-league pitching coordinator, approached Matz about throwing instead of a slider before the 2013 season. Matz said he still is "getting a feel for'' the pitch.

"I don't think he would have ever thrown a curveball in that situation last year,'' said Viola, who pitched for East Meadow High School and St. John's, went 24-7 for the 1988 Twins in winning the Cy Young Award, compiled a 20-12 record for the 1990 Mets and now is the Mets' Triple-A pitching coach.

"His first thought would've been fastball because that's all he's needed to put guys away,'' Viola said. "He didn't have enough confidence to throw the curveball in a key spot. But I knew it was just a matter of time before that would change.''

Now the curveball is one of the reasons Mets vice president of player development and scouting Paul DePodesta recently called Matz a "gem'' in the farm system. "His curveball has come a long way this year,'' he said.

What's suddenly become so important in Matz's development is something he never needed before. His fastball, which sits at 92 to 94 mph with late movement, has always been more than enough. Until now.

Prodigy

Matz, who is 23, fired his first fastball when he was 2 years old. Ron Matz looked at his wife, Lori, and told her, "We might have something special.''

When Matz was 10, he started receiving pitching lessons from Neal Heaton, the former major-league pitcher from Sachem High School. Heaton would look at Ron Matz and say, "This kid is going to be a big-league pitcher.''

Ron Matz would respond by laughing and calling him crazy.

Ron Matz first saw his son's fastball timed in June 2008 at a showcase for college and pro scouts in Connecticut. Matz, who had just completed his junior year of high school, had just experienced a growth spurt of about five inches (he's now 6-5).

Matz threw the first pitch. The radar gun read 90 mph. A crowd gathered. Matz threw the second pitch. The radar gun read 90 mph. The crowd grew.

"He displayed that fastball, a gift from God,'' Heaton said.

Back then Matz didn't need to change speeds. "He did try to pick up the breaking ball right away,'' Heaton said. "But it's something that's really hard to understand the importance of until you go out there, throw your 95-mph fastball and see it get turned around.''

That never happened in high school, Ward Melville coach Lou Petrucci said.

The most impressive thing about Matz back then -- besides the fact that he never was a second late for a 6 a.m. practice -- was that Matz's fastball velocity usually stayed at 90 mph in the late innings, Petrucci said.

"His fastball was something else. His curveball was devastating in high school, but he didn't need to throw it,'' he added. "Nobody signs you in high school for your curveball. They sign you for your fastball, body and attitude. Steven had all three.''

Breakout in 2013

Matz did not make his pro debut until 2012 because of a bumpy rehab from Tommy John surgery in 2010. But he put himself back on the radar with a strong 2013 campaign for Class A Savannah, going 5-6 with a 2.62 ERA in his first full season. He struck out 121 batters in 1061/3 innings, mostly because of his live, overpowering heater.

It was with Savannah, Viola said, that Matz made progress with his secondary pitches. "The thing he did so well last year was he picked up the changeup,'' Viola said. "He was on a mission, basically. It became a 'plus' pitch in a short period of time. The one pitch that he had to work on was the curveball.''

Still, as long as Matz's fastball overwhelmed the lineups in Class A, his off-speed stuff took a backseat.

"His fastball is such a good pitch that it almost makes it harder for him to develop his secondary pitches,'' DePodesta said.

Viola said he never had an issue with Matz accepting the responsibility that comes with developing pitches, but he added, "I guarantee you in the back of Steven's mind, he was going, 'What is going on here?' Because there's always doubt. There's always going to be doubt until you see results.''

Earlier this season, Matz went 4-4 with a 2.21 ERA in 691/3 innings for Class A St. Lucie. But in his first Double-A start with Binghamton on June 27, he allowed five earned runs and seven hits in 52/3 innings.

In reference to a curveball he left high in the strike zone that got smoked for a double, he told pitching coach Glenn Abbott, "Wow, I'm not in St. Lucie. Down there, they'll take that pitch or pop it up.''

"That's the whole thing,'' Abbott recalled telling him. "When you move up in baseball, guys have experience and these pitches you throw have to be better. You can't just rely on fastballs out of the zone.''

Finding consistency

Abbott said Matz's curveball has become "more and more consistent'' since that first start. The results have followed. Matz is 4-2 with a 3.27 ERA in 411/3 innings with Binghamton.

"The biggest thing is the curveball and trusting it,'' Abbott said. "We've been stressing the curveball more in bullpen sessions, and even if the ball-to-strike ratio isn't that good [it's about 1:1], the quality of the curveball is much better.''

Earlier this season with Binghamton, Matz would throw only six curveballs per 25-pitch bullpen session. Now he throws about a dozen, Abbott said. Said Matz, "Especially at this level, you really need that third pitch.''

DePodesta said it's standard practice for the club to mandate a certain quota of a given pitch for a pitcher to hit per start. The best thing about Matz, DePodesta added, is his understanding of how important it is to believe in his other pitches.

"The fact that he's actually taking the time and energy to really try to improve his secondary pitches says a lot about him and his maturity,'' DePodesta said. "Because at some point he knows that he's going to need these as weapons and be able to use them interchangeably at any time, in any count.''

The way he did in that start against Portland. "You should've seen the fans looking at me because I was screaming so loud,'' said Ron Matz, who was at the game. "It was just awesome.''

Viola didn't attend that game. He hasn't seen Matz pitch since last year, but when he was told that Matz finished off back-to-back batters with a curve, he said, "Well, that just made my day.''

He added, "The fastball has always been there, the changeup got there, and the curveball is going to be a 'plus' pitch as well. That will be three 'plus' pitches, and that makes for a big league career for a very long time.''