Michael Pineda has always had a bit of a weak spot in his pitching profile. From his debut in 2011 until his 2017 ended with Tommy John surgery, he threw 680 innings while allowing 91 total home runs. That translated to a 1.20 HR/9, putting Pineda in the bottom 20th percentile in the league among pitchers with at least 650 innings pitched.

Despite the eye-catching rate, the home runs were a manageable issue; Pineda’s FIP in those years was a fine 3.60. More than avoiding home runs, Pineda needed the health he enjoyed between 2015-16 to be an average starter. Even setting aside the Tommy John, his time in the majors is riddled with stints on the disabled list for a variety of maladies. Now in 2019, with the health of his arm finally restored, the home run issues looms larger.

After his first nine starts of the year, Pineda is leading the majors in home run rate among qualified pitchers with a 2.49 HR/9. Following his last start, he became the first Minnesota Twins pitcher to allow at least three home runs in consecutive outings since Bartolo Colon in 2017.

This is still a small sample, and Pineda’s home run rate will probably go down as he keeps pitching. However, given his previous home run issues, the recent spike merits a closer look.

First, let’s examine his fastball. Of the 13 home runs he has allowed this year, six have been against fastballs in the middle or upper part of the zone. Pineda has always liked to throw his fastball in the zone, challenging hitters with good gas, and he has been doing exactly that this year.

Have a peek at the location of his fastballs prior to 2019:

And here they are so far in 2019:

A few more pitches arm-side and few more pitches middle/middle, but generally speaking, it looks similar.

The thing about Pineda’s fastball this year is that it has lost 1.8 mph of average velocity when compared to his 2017 four-seamer (92.1 mph vs. 93.9 mph), and, perhaps more importantly, his spin rate is now really working against him pitching up in the zone.

Let’s look at the list of the fastballs with the lowest average spin rate in 2019 among starting pitchers:

The fact that Pineda has lost a tick on his fastball and now ranks near the bottom of the spin rate leaderboard doesn’t match up very well to his tendency to challenge hitters in the middle part of the plate or up in the zone. That pitch, if it sustains its current specs, will probably continue to suffer if it’s thrown to that area.

A quick look at Statcast since 2015 tells us that four-seam fastballs with a 2000-rpm spin rate or lower that are pitched in the middle/upper part of the strike zone have had an xwOBA of .381. If the fastball has more than 2000 rpm of spin, the xwOBA lowers to .339. If it has more than 2300 rpm of spin, the xwOBA lowers to .324. And if it spins at more than 2500 rpm, the xwOBA lowers to .304.

Because spin rate and pitch velocity tend to correlate, the same happens with xwOBA as the average velocity creeps higher. But in Pineda’s case, it’s not the same to challenge hitters with a 92.1-mph average fastball as it is to do so with a heater that has an average spin rate of 1999 rpm. One of those is a bit more dangerous for the pitcher.

What pitchers in Pineda’s situation tend to do (if they want to survive in the majors) is to work lower in the strike zone and develop a secondary pitch that helps their fastball get some strikes in the zone.

Maybe Pineda’s power changeup can do the work of a sinker. After all, it’s a power changeup (less than 6 mph of separation with his fastball) and has good fade, and he uses it only 5.1% of the time against right-handed batters. But that pitch doesn’t generate ground balls (31.6%), and Pineda would likely welcome a pitch that elevates his current 32.9% ground-ball rate.

Maybe he could go for a sinker: According to Brooks Baseball, he threw 23 in 2011, two in 2013, five in 2015, two more in 2016, and four in 2017. But it looks like he never decided to make this pitch a part of his traditional repertoire.

Or maybe he could try develop a cutter. He wouldn’t be the first starting pitcher with fastball issues to do it in recent years: CC Sabathia did it in 2015, Anibal Sanchez managed to do it in 2017, and even his own teammate Martin Perez did it in 2019, just to name a few.

Then again, the home run problem Pineda has suffered from this year isn’t just a fastball thing. Let’s take a look at his slider. As his money pitch, his slider has resulted in almost half of his strikeouts, but things have been very messy when he throws it in the zone.

Here is the bottom of the xwOBA leaderboard on sliders in the zone this year:

Pineda’s slider has been absolutely demolished when it’s thrown in the zone, ranking as the very worst one in MLB. He has allowed five home runs and a 93.0-mph average exit velocity with it. When it’s thrown out of the zone, things change dramatically, as they should: a .162 xwOBA.

But the answer can’t just be a “throw your slider out of the zone” approach, can it? Hitters will adjust, stop chasing it, and very soon the Pineda Home Run Thing will become a Walk Thing, right? Well, the numbers tell a different story. Walks and control have not been an issue for Pineda this year. Right now, he has a 4.5% walk rate and a 46.6% zone rate (12th among qualified pitchers). Those numbers could suffer a bit in order for him to avoid barrels and home runs.

Another suggestion that a change of strategy could possibly be successful is the fact that hitters are swinging at his slider at a 54% rate. He is not the leader in that category, but he is 25th among 150 pitchers with at least 100 sliders thrown. This aggressiveness could be used by Pineda for generating whiffs out of the zone and avoiding hard contact with his breaking ball.

There are plenty of examples of pitchers that throw most of their sliders out of the zone, don’t have particularly overpowering velocity on the pitch, and generate a healthy amount of swings. In fact, his teammate Kyle Gibson is the poster boy of this trick, offering only 25% of his sliders in the zone and producing a 50% swing rate. Julio Teheran is another case with a 35.5% zone rate on his slider and a 49% swing rate. Patrick Corbin does something similar with a 30.1% zone rate and a 50.7% swing rate.

Of course, successfully executing these types of adjustments is not an easy thing to do, and it is even trickier to pull off in the midst of a season. Then again, the home run spree that Pineda is suffering right now will probably remain as a real and constant problem if he doesn’t evolve and change according to his new stuff on the mound.