The Mejia Reality: What's The Big Deal About This "Reliever" With The Mediocre Numbers? (A PitchFX Story)

(I meant to bump this to the front page earlier but some other things got in the way. Even though Mejia has been demoted the findings here are still relevant. --Eric)


Jenrry Mejia is a very polarizing figure. Management (or at the very least Jerry Manuel) still likes him in the bullpen for mop-up work. Fans want the 20 year old to return to the minors as a starter so that the Mets' top (or near-the-top) prospect can develop.

Yet for a top prospect, the results don't seem to be that impressive aside from his 3.38 ERA. Mejia's 4.92 FIP shows that the low ERA has probably resulted from a lot of luck and his 5.40 K/9 is, well, not what you'd expect from a top prospect with a 95MPH fastball. Even worse is his 5.06 BB/9, which shows his considerable lack of control, and his -0.2 WAR (according to Fangraphs) which ranks him as WORSE than a replacement player this year! He does have a terrific 66.7% GB%, which is very positive and a good sign for the future, but the walk rate offsets even that little advantage. Clearly, the kid shouldn't be in the majors right now.

And yet this is not to say that the kid hasn't shown results that should get Met Fans very excited for the future. After the jump I'll take a look at Mejia's pitches and show that while his pitches are indeed very raw and in need of refinement, they show tremendous promise.

Mejia's Pitch Repertoire

*Note: All Results below are from Mejia's pitches through June 11, 2010. I don't think any of the below changes due to his two appearances since that date.

Jenrry Mejia is known to throw four pitches: A four-seam fastball, a two-seam fastball, a change-up, and a curve-ball. The four seamer can be seen on the graphs below in addition to a variant of the four-seam fastball which seems even more cutter-like (and thus I'll refer to it as a "cutter" for the rest of this article).

(CLICK on the image for a better view of the graphs)

Figure 1 and 2: These two graphs show the movement and speed of Mejia's four pitches. The graphs are from the catcher's point of view, so the more right a pitch is (and the more positive its horizontal movement), the more in on left-handed batters that pitch moves (and away from right-handed batters). The vertical movement (Y Axis on the graph on the left) measures the additional drop of a pitch once gravity is taken into account. Thus a pitch with +10 vertical movement drops 10 inches LESS than we would expect it to while a pitch with -10 vertical movement drops 10 inches MORE (like a curveball).

The blue dots on these graphs are curveballs, the green dots are change-ups, the yellow dots are two-seam fastballs, the red dots are four-seam fastballs, and the orange dots may be a third type of fastball that I've labeled a cutter* (*More on this below*)


Figure 3: The above graph shows the pitch track of each of Mejia's pitches from the point of view of a catcher behind home plate. The black box is a rough approximation of the strike zone. Thus a catcher who views each of these pitches will see the pitches follow the above paths.

NOTE: I have slightly altered this graph so that it is easier to see the different movement of each type of fastball by showing how each fastball aimed at the same location would move.

This graph uses the same legend as above: The blue track is his curveball, the green is his change-up, the yellow is his two-seam fastball, the red is his four-seam fastball, the orange is the "cutter." The purple pitch track simply shows the average RHP's four-seam fastball's movement and is meant for comparison.

In addition to the graphs above, here are the average movement and velocity statistics of the pitches shown above (feel free to skip these if you want, they just show in numbers what the graphs show above.)

Pitch Type Average Horizontal Movement (Inches) Average Vertical Movement (Inches) Average Velocity (MPH) Standard Deviation of H. Movement Standard Deviation of V. Movement
Change-Up -4.147 +4.314 86.83 2.79 2.079
Curveball +3.926 -8.029 79.46 2.68 2.533
Cutter* +2.189 +2.152 94.31 0.998 1.498
Four-Seam +0.403 +5.289 95.13 1.36 1.889
Two-Seam -3.3344 +4.327 94.97 1.54 2.05535028
Average RHP Four-Seam -5.366 +8.808 91.92 ------ -----

*The pitches I'm describing as a cutter are 50 pitches that (as you can see on Figure 1 above) have even greater cutting movement and drop than the normal four-seam fastball. Still, nothing I've read suggests that Mejia throws a third fastball and's Toby Hyde and I think that this pitch is probably just random four-seam fastballs that result in this extreme movement. That said, I have separated the data on these pitches out from the other four-seam fastballs for the moment.

So what do these graphs and the table above show us? Well, what we should expect from our top prospect: his stuff looks really good. You'll notice that in addition to being around 3-4MPH faster than the average fastball, Mejia's four-seamer has about 3.5 inches more downward movement. This is part of why Mejia is able to achieve his great ground-ball rate. The pitch described above as a "cutter" has an even greater drop (it drops 6.5 inches more than the average four-seamer, resulting in an extreme ground ball rate of 70%). The two-seam fastball and his change-up also have better-than-average "sink" (about 1 inch lower than his four-seamer), complementing Mejia's four-seam fastball.

In addition, you'll notice that both Mejia's four-seam fastball and his "cutter" seem to have an awfully straight trajectory. Isn't that a bad thing, you might wonder? Actually, no. Most cutters/cut-fastballs have an essentially straight trajectory, and this is a positive thing because batters are used to fastballs having some tailing action (as seen by the average fastball shown in Figure 3 above). The end result is that the pitch goes more away from right-handed batters and inside on left-handed batters than they expect it will, further resulting in poor contact.

The bottom line is that his fastball has above average velocity, above average sink, and a strange horizontal movement that should baffle hitters for years to come. It is indeed pretty exciting.

His change-up has a similar movement to his two-seam fastball, but is around 8MPH slower, a satisfactory amount. His curveball also has a nice drop and velocity (79MPH on average is a nice curveball). However, you'll note on the graph above that his release point for his curveball is indeed quite different from his fastballs or change-up. It's hard to tell if this is a problem yet, as it's not quite AS blatant as seen in Jon Niese's curveball and as a reliever, Mejia isn't throwing the curveball that often (only 34 curveballs out of 451 pitches (7.5% of the time)). It's probably not a huge problem, as Mejia's curveball is unlikely to become (ever, really) his primary out pitch.

Mejia's Performance

Now we that we see that Mejia's pitches have some great movement and velocity we must ask the question: Why has his performance been so poor? The table below shows why:

Pitch Type Run Value Against LHBs* Run Value Against RHBs* Percentage of Pitches thrown for Balls (LHB) Percentage of Pitches thrown for Balls (RHB) GroundBall % (LHB) GroundBall % (RHB) Line Drive % (LHB) Line Drive % (RHB)
Change-Up -0.8072 -1.1353 53.6% 38.3% 57%** 100%** 14.2%** 0%**
Curveball +0.119 -0.2208 14.2% 55.1% 100%** 60%** 0%** 0%**
Cutter -0.3881 +2.055 23.8% 34.5% 50%** 75% 0%** 0%
Four-Seam -0.9337 +1.386 33.3% 41.3% 69% 50% 23.1% 35.3%
Two-Seam -1.4993 -1.1765 29.2% 31.4% 100%** 87.5% 0%** 12.5%

*A quick reminder: NEGATIVE run values are good for pitchers (they mean that the pitcher saved that many more runs than the average pitcher would with those pitches) while POSITIVE run values are poor (positive run values indicate a pitcher gave up more runs than an average pitcher would have).

**The ground ball and line drive percentagess with two asterisks next to them have such a small sample size (from 1-7 balls put in play as to make these percentages meaningless).

First of all, we can see from the run values that Mejia's biggest problem has been his four-seamer and the "cutter" variant of that four-seamer against right-handed batters. His other pitches are at the very least average. Now why are these pitches so poor? Well the "cutter" has been poor because two of the "cutters" put into play by batters have resulted in home runs. That hurts that pitch a lot. Otherwise, the "pitch" (if it is a separate pitch) has been fine, resulting in mostly ground balls as expected.

The four-seamer has numerous problems. Against right-handed batters, Mejia is missing the strike zone too often. Moreover, the pitch is not working the same ground-ball magic as his other pitches, with a huge 35.3% of balls hit off of it resulting in line drives. As you can guess, line drives are considered the most unfavorable type of batted ball type because they almost always result in hits.

Mejia's control of his other pitches isn't terrific either; his curveball against right-handed batters more often than not results in being called for a ball while his change-up against left-handed batters suffers from the same problem. The result is that these pitches get him into worse counts where Mejia has to use his fastballs, which have not been particularly successful this year. This has resulted in the elevated walk rate (as the four-seam fastball hasn't been that accurate, as noted above) as well as too many balls being hit well off the ground.

The Future of Mejia:

Mejia should be sent down to the minors to work on his stuff as a starter. We all know that. But in particular, for him to realize his potential, he's going to need to work on several specific things:

First, and most obviously, he needs to work on his control. He should not be having 40% of his four-seam fastballs to right-handed batters being called for balls at the very least, and his off-speed stuff's accuracy could stand to improve as well.

Secondly, in order to achieve his goal of improving his command, he probably needs to get better control over how his pitches move. Mejia's normal four-seam fastball sometimes acts as a clear cutter (the pitches I've called a "cutter" above) and sometimes acts like his two-seam fastball and looks more like a normal fastball. The movement is all over the place. This almost certainly affects his accuracy (if he doesn't know if his fastball is going to break toward right-handed batters or not, it can't be easy to aim it properly) and can probably be fixed through constant repetition and throwing more and more fastballs as a starter in the minors (I can't imagine the work as a reliever helping this cause). Mejia needs to do this for his change-up and curveball as well.

Finally, Mejia might want to try to adjust his release point of his curveball so it's closer to his normal release point, but this should be the lowest priority of things to do for his development. He's not a predominantly curve-ball pitcher and the pitch is never going to be his biggest weapon. He should still work on the pitch, but shouldn't go crazy trying to fix it.

All in all, Mejia is a very fascinating prospect. He has, as said above, a fastball that can be a terrific weapon for him for years to come if he can improve its accuracy and his consistency with the pitch. His change-up's movement is great as well, and the curve-ball shows promise. This is what we need to remind ourselves of every time we see him wasted giving up walks in the bullpen in mop-up duty: he has the potential to be much better than that, if the Mets would just give him the chance to develop.

This FanPost was contributed by a member of the community and was not subject to any vetting or approval process. It does not necessarily reflect the opinions, reasoning skills, or attention to grammar and usage rules held by the editors of this site.

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