SCOTTSDALE, Ariz. – Beyond the technology that measured the spin rate, axis, pitch shape and release point, all of which suggested that it would beneficial to try something different, there needed to be trust. Besides the results of the past few seasons, and the constant battle to find consistency with a pitch that just didn’t want to be harnessed, there needed to be conviction.

Those two aspects, both immeasurable by empirical data, remained vital for this sort of drastic change to work at this point in spring training and at this key time in Justus Sheffield’s young baseball career.

They are two words used often when discussing pitching success. And one doesn’t work without the other.

Sheffield needed to trust what pitching coach Pete Woodworth was suggesting, a change based on the data accumulated and past results and that it would be beneficial to him, and additional trust in what catcher Tom Murphy was seeing behind the plate on every pitch in bullpens that this was indeed real. Because without that trust, there would be no way Sheffield could embrace and execute it with proper conviction needed for real success.

If all this works for the better as the Mariners hope, then Sunday’s spring-training outing against the Giants at Scottsdale Stadium could be a seminal moment for Sheffield’s future and an oft-recalled anecdote to highlight the collaborative process that is player development.

In three innings of work, when Murphy called for a fastball, Sheffield threw one – but with a completely different grip and a much different intent.


“I was throwing all two seamers today,” Sheffield said proudly.

The results: Sheffield pitched three innings, allowing one run on three hits with no walks and five strikeouts. And that one run could’ve been avoided if J.P. Crawford makes a better play on a ground ball with two outs.

“It was an outstanding pitch,” manager Scott Servais said. “His ability to locate it is huge. At the bottom of the zone, it plays really well … and it sets up the slider so well.”

This might not seem like major news, but to a pitcher it’s significant. Sheffield had thrown nothing but four-seam fastballs for his entire career. And at the suggestion of Woodworth, some prodding from Murphy, and input from the baseball operations staff, Sheffield began experimenting with a two-seam fastball about 10 days to two weeks ago while playing catch and throwing in bullpen sessions.

“He just trusted something he could do naturally and he’s been working on it for a couple of weeks and today was the first game where he said let’s do it and see what it looks like,” Woodworth said. “That was the best fastball and fastball command I’ve seen him have.”

A four-seam fastball is held across the wide horseshoe of seams on the baseball with two spread fingers. The intent is to use all four seams to generate backspin while throwing it with maximum velocity, which helps the ball maintain speed and sink at a slower rate due to gravity.  The two-seam grip is held with the fingers closer together on or just inside the narrowest part of the seams. The decreased spin generated will usually take a few mph off the speed of the pitch, but also cause it to have a late sinking motion beyond gravity as it gets close to the plate.

“There wasn’t much selling,” Woodworth said of the initial conversation. “I feel like Justus and I have a good relationship. The main thing he’s working on is fastball command. We just saw with the four-seam that he’s been working on it awhile and it’s what he’s always thrown, but his other pitches were off his two-seam grip and that’s kind of contrasting ideas. The first time he put the two-seam grip in his hand, he said, ‘This feels great.’”


It felt natural to Sheffield and it kept him mechanically sound.

“I started messing with it and I really liked it,” he said. “It helped me mentally to stay closed in my mechanics because you are thinking you have to stay closed to get that pitch sinking and moving.  I’m a pitcher that if I fly open, it’s not a good day. This keeps me on track and closed.”

To Murphy, who looked at the data and also had to try to corral Sheffield’s unpredictable four-seam fastball in the past, this seemed like a logical change. He mentioned it to Woodworth after Sheffield’s first bullpen of the spring.

“His four-seam had very low spin to begin with, so him switching to a two-seamer actually is going to benefit him in the long run, and you saw that today,” Murphy said. “It’s one of those things where you kind of want to feed the beast, right? If a four-seam isn’t necessarily at the upper echelon, then why keep pushing something that isn’t going to be a great pitch? When you can make it a two-seamer, now all of a sudden, that low spin rate plays to his advantage.”

Ah, spin rate, the new key data piece in MLB pitching. Pitchers that throw four-seam fastballs want high spin rate. High spin rate gives their fastball the appearance it’s almost rising. It makes their fastballs more difficult to hit on the barrel or even touch. A four-seam fastball should have a spin rate from 2,200 to 2,600 revolutions per minute. A two-seam fastball should have spin rate of around 1,900 to 2,200 RPM for maximum success.

Sheffield’s average spin rate on 340 fastballs thrown last season in his eight MLB appearances was 1,835 rpm — one of the lowest of MLB starters. By comparison, lefty Mike Minor averaged 2,650 RPMs on his four-seam fastball while Justin Verlander was right behind him at 2,574.


Murphy was beyond complimentary of the new pitch. The unpredictability of the four-seam fastball was replaced by actual command to both sides of the plate with the two-seam.

“At times, his four-seam did whatever it wanted to do just because of the low spin,” Murphy said. “It wasn’t as consistent as what I saw today (in the two-seam). Today’s movement was the same every time, which is very good.”

Where the two-seam was noticeable is that the natural movement tends to go away from right-handed hitters. Per the stadium radar gun, Sheffield’s velocity on the two-seam fastball was still around 92-93 mph. Add to that a change-up that also tails away from right-handers and a nasty slider – his best pitch — that he throws in and at their back foot, and Sheffield should see increased strikeouts.

“It’s huge,” Murphy said. “Doing that against a righty makes the plate seem 20 inches wide instead of 17. He can go three inches inside to a righty and run that two-seamer back (on the plate) and now the right-hander has to respect a larger portion of the inner-half of the plate and he can bury the slider even deeper.”

So will he scrap the four-seam?

“I’m going to start throwing the two-seam a lot, just for more movement and give a different look to the hitters,” he said. “My four-seam gets run already. Why not change to the two-seam grip and get some more run. I’m definitely going to keep the four-seam to get that spin rate up and throw it at the top of the zone. But that’s for a little bit later down the road and where we’ll mix it in.”

For now, Sheffield just wants to throw strikes with it.

“Right now, I’m not looking at the movement,” Sheffield said. “I’m just seeing the glove and throwing it to the glove. Whatever it does when it leaves my hand is what it is. It’s moving down and working down in the zone. It’s got me excited. Learning the pitch that quick and being able to throw it out there. I just have to keep throwing it.”