In a season with few positive notes for the Minnesota Twins, one had to be Scott Diamond's breakout. On April 6th, Diamond was barely an afterthought; he had been selected in the previous year's Rule V draft and stashed in AAA where he failed to impress anybody, pitching himself to a 4-14 record with a 5.56 ERA in 2011.

By May 8th, Diamond had generated some buzz, starting 6 games and allowing just 12 runs in his third season in AAA. His first major league start was a resounding success as he pitched 7 scoreless innings. The rest of 2012 went much the same way, Diamond became the Twins most reliable starter. Wait, that's barely a compliment given the Twins' rotation options, let me rephrase that. Diamond became an above average starter in the American League.

Diamond's success comes with plenty of questions though. For one, how did he do that? Another, what do we know about the pitcher himself? And lastly, what can we expect out of him in the future?

The Numbers

The easiest entryway into this case study is to look at what Diamond accomplished in 2012. He started 27 games netting 173 innings (207.2 including AAA time). In that time, the Canadian lasted at least five innings in all but one start. Diamond recorded a 3.54 ERA, well below the league average of 4.08. His FIP (3.94) and xFIP (3.93) tell slightly stories, though still impressive.

These numbers reflect a few very good underlying skills, namely his control and groundball ability. Diamond led the American League yielding 1.6 unintentional walks per game and never allowing more than 3 in any outing. On top of that, Scott was able to induce 53.4% groundballs when the ball was put in play. For context, that's tenth in all of baseball.

Diamond was able to translate these two elite (and very Twins-pitcher-like) skills into a nice season, despite a 4.7 SO/9 rate (2nd worst in the AL). Few pitchers, if any, are able to have sustainable success with such low K-rates, so his ability to miss bats going forward will be something to watch.

Interestingly, the statistics that are often correlated with luck don't discout Diamond's success in 2012. His babip, .292 is not out of line, especially for a ground ball pitcher and his HR/FB percentage of 11.4 is also right about average as is his strand rate (73.3%). These data suggest Diamond's breakout isn't a total mirage. The extent to which he regresses will be largely a function of his striking out a few more and continuing to avoid giving up free passes.

The Repertoire (almost all data from BrooksBaseball.net, great resource)

• Four-seam fastball (90.00 mph)
  
• Slider (81.99 mph)
  
• Changeup (84.35 mph)
  

Scott Diamond relied heavily on his fastball in 2012, throwing it 60% of the time. The pitch rarely got any swings-and-misses (2.79%) but resulted in groundballs 13.42% of the time and was located well as only 36.07% of them went for balls.

Diamond's slider was primarily an out pitch, used mostly when he was in the count. Surprisingly, the slider was also a deadly accurate weapon, only 28.43% of them resulted in balls. Not so surprising is that the slider produced the most whiffs of any of his pitches (15.05%).

The change-up was used almost exclusively against righties, about 16% in those situations, and only five times all year versus a lefty. The pitch yielded more whiffs than his fastball but didn't get as many grounders. All this leads me to believe that his change-up is more a "show-me" pitch than anything else.

When put all together, Diamond's repertoire is pretty simple: a two pitch mix against lefties and three against right-handed hitters.

A lot of Diamonds success comes from his ability to pound the lower, inside half of the strike zone (as shown below) resulting in a lot of groundballs.

Interestingly, Diamond's fastball actually ticked upwards from 2011 to 2012. He gained about 0.5 mph on his fastball and 1.5 mph on his slider. There are many possible reasons for the uptick: weather or increased stamina and strength to name a few. These are all likely causes of the uptick, however, they cannot be measured. Of factors that can be measured I found one interesting change from 2011 to 2012: his arm angle.

As seen in the chart below, Diamond lowered his arm angle (roughly 3-4" out and 2-3"down).

My initial feeling on this was a bit of confusion. Usually pitchers with lower arm angles don't throw as hard, at least that's my perception. I e-mailed Andy about his thoughts on the change and corroborated my belief that the change would add movement to his slider, but he also had some other enlightening idas on the subject. Particularly, that lowering the arm angle could free up his motion and actually add velocity to his pitches.

With this knowledge, it's a little easier to accept that Diamond has truly "broken out" to some degree. Under the basis of changed mechanics, more velocity and increased control, Diamond was able to change (or enhance) his skills as a pitcher

The Future

Predicting the future of a pitcher is impossible, but given what we do know, we can make a fairly good guess. Diamond's basic skills of control and ability to get groundballs are likely here to stay, however, his inability of striking out batters is very troubling and will absolutely limit his upside.

In fact, I think we saw Diamond's upside in 2012. That isn't to disparage his future, Diamond was very good for the Twins last season and could have been #2 or #3 starter on many teams. It is likely that Diamond will regress towards a league average 4.00 ERA predicted by FIP, xFIP and SIERA (all ERA estimators).

Sadly enough for the Twins, a league average pitcher could be their ace in 2013 given the current outlook, making Scott Diamond an invaluable piece to puzzle. However, nobody should expect him to make significant strides from the success of his first full season.

cross-posted on PitchersDuel.blogspot.com