Having such a small sample size (16 batters faced over four outings), and struggling badly in three of those appearances makes any attempt at statistical analysis on results difficult. His ERA is 48.60, his FIP is over 15, and his WHIP is 6.6 (SIX POINT SIX!). There's nothing to conclude or analyze here, other than stating the obvious, which is that Brayan Villarreal has been bad.
A bit of it can certainly be attributed to bad luck. His BAbip is .833 (again, extremely small sample), and 50% of the fly balls he's allowed have been home runs – most players can't average 50% home runs in batting practice, let alone game situations. But those numbers leveling out still don't address his suddenly hittable repertoire, and his lack of command or even control of the strike zone.
This control issue isn't something that just popped up however. In fact, it very clearly started toward the end of last season, when after posting a 3.1 K:BB ratio for much of the season, the bottom fell out in the final month, and he walked more batters (nine) than he struck out (seven). That trend has continued as he has once again walked more than he's struck out this April.
The pitches illustrate that as well – last September, he threw 87 strikes to 79 balls. Thus far this season, he's thrown 43 strikes and 35 balls. Compare that to the rest of 2012, when he threw 514 strikes compared to 260 balls. A healthy 2:1 strikeout to ball ratio collapsed to nearly 1:1 seemingly overnight (In August 2012, he 135 strikes and 69 balls).
Villarreal did have the one good outing to start the season in Minnesota, striking out two batters while allowing a hit, however, even then the control wasn't masterful – in 16 pitches, he tossed 7 balls and 9 strikes.
His velocity is also down so far to start the season, and it's notable too. Cold weather certainly could potentially impact that, but after seeing his fastball average 97.1 MPH last year, his velocity is sitting at 94.9 MPH on average so far in 2013. However, his velocity at the end of 2012 was around the norm for 2012 (around 97-98 MPH). It's easy to think the dropped velocity is suddenly making him more hittable, but for example, last September 28th against the Minnesota Twins, Villarreal was dialing his fastball up to 98 MPH, but he walked three and allowed a hit in one inning of work, throwing just 12 strikes in 28 pitches.
Utilizing Pitch FX data, we can see just what is happening with Villarreal's pitches on a game by game basis. Some might hypothesize that Villarreal's being scouted better, and as a two pitch pitcher featuring a slider and a fastball, never controlled the zone that well, and players just needed scouting information to guide them to lay off certain pitches. The data paints a different picture however.
Taking a look at Villarreal's scatter plot from a rather effective appearance from last year, August 24th against the Angels, we can see that Villarreal had no trouble finding the strike zone. Of the 26 pitches thrown, 23 were strikes, and just seven were clearly outside of the zone. Villarreal was dialed in here.
Looking at Villarreal's release point, he was very consistently clustered, stretching from 5' 6" up to 6' (remember Villarreal is listed as a generous 6' 0", more likely 5' 10"), with a horizontal point right at 3 feet.
Now, compare that release point to Villarreal's second appearance of the season this year against Minnesota, in which he allowed five runs, yielding four hits and walking two while recording just two outs. What we see is a very stark contrast. A much lower release point (clustered between 5' and 5' 6", averaging about six inches lower compared to his appearance last August against the Angels), and much greater horizontal variance, spanning nearly a foot around the 3 foot out mark.
No surprise, his ability to control the strike zone disappeared, with 15 pitches outside the zone.
Taking a look then at his next appearance against the Blue Jays in which he walked three batters, the release point looks much closer to his previous appearance against Minnesota than the 2012 graph against the Angels. The horizontal variance is now concentrated all outside of 3 feet, and the height maintains right around 5' 6", still nowhere near the downward action of a 5' 10" reliever coming down at approximately the same height (as opposed 4-10 inches lower).
And finally, that aforementioned difficult outing last September against Minnesota? It's almost a mirror image to the Blue Jays appearance, with horizontal range all outside of 3 feet, and release point height consistently at around 5' 6".
This analysis won't dissect Villarreal's motion and delivery and diagnose what needs to happen to fix it, but what appears clear from this analysis is that something has gone awry in Villarreal's mechanics, resulting in a lower and more varied release point, causing him to lose command of his ball and preventing him from consistently throwing strikes.
Quick tweaks are possible, but more likely; this will take some deliberate work in making changes to a delivery that needs some help to get Villarreal throwing strikes again. Those sorts of modifications should happen away from big league hitters in the comforts of Triple-A Toledo, where Villarreal won't have the big league pressure on him. For that reason, it's time for the Tigers to option Villarreal down and give another reliever a look in the meantime.