Of the 133 qualified relievers this season, only two have managed to compile walk rates better than one per nine innings pitched. Those two are Edward Mujica of the Padres and tonight’s featured pitcher: Wilton Lopez of the Astros. Lopez’s 0.73 BB/9 rate in 62 IP leads all relievers, and it makes him a rarity: a productive reliever who doesn’t rely on the strikeout. Lopez is the only reliever in the top 25 in reliever FIP to with a strikeout rate below 7.0 K.9.
Rate starts are nice, but when it comes to players like Lopez, it can be easier to understand just how well they are pitching with raw numbers. Lopez has walked only five batters all season of the 244 that have faced him, and that includes one intentional walk.
Lopez “pounds the zone” to a degree, to use a favorite cliche of announcers. According to Pitch F/X data, Lopez hits the strike zone with 51.6% of his pitches, a mark exactly five percentage points above the league average. That puts him in the upper echelon of qualified relievers, ranking 11th. However, simply hitting the zone often is no guarantor of limiting walks. The walk rates of those in the top 10 in zone% range from 1.25 (Rafael Betancourt of Colorado) to 4.09 (Robinson Tejada of Kansas City), and although we see more in the 1-2 range than 3-4, there’s more to avoiding walks than simply hitting the zone.
The key, at least for Lopez, appears to be the ability with which he can draw strikes with both his two-seam and four-seam fastballs. Lopez has thrown 448 four-seamers and 244 two-seamers this season, and both pitches have fallen for strikes over 68% of the time, whether it’s of the contact, called, or swing-and-miss variety. It should come as little surprise, then that when we take a look at his pitch selection by count, his go-to pitch has been one of his fastballs.
In the six (!) 3-0 counts that Lopez has seen this seasons, he’s thrown the four-seamer four times (three strikes), and the two-seamer twice (both strikes). In the eight 3-1 counts, we see seven fastballs (five strikes) and one changeup (for a strike). Lopez has thrown a more substantial 20 pitches in a full count this season. Again, the fastball has been prominent, featured 18 out of 20 times and thrown for a strike a remarkable 17 times. He’s also gone to his other two pitches, the slider and the changeup, one time each, with the result each time being a foul ball.
Most remarkably, of the 20 pitches Lopez has thrown in these full counts, 18 of them have drawn swings. Only two of them have been whiffs, but it’s still remarkable that only twice have hitters even left it up to the umpire to call the pitch a ball. When we take a look at the location chart from Texas Leaguers.com, we see that Lopez has been near the zone with a majority of his full count pitches.
These graphs aren’t perfect at predicting an umpire’s call based on location, but I wouldn’t bet that 90% of these pitches would be called strikes, and swinging 90% of the time or higher is likely far from the optimal strategy. That said, most of these pitchers are close enough that it wouldn’t be worth leaving the decision up to the human umpire. Lopez’s excellent control with the fastball – roughly 10 percentage points more strikes with his fastball than the league average – keeps hitters on their toes and expecting strikes.
Lopez has been extremely successful as a reliever this year, posting 1.2 WAR to date, and there’s no reason to think that he can’t continue this success. His arsenal – particularly, the presence of a changeup – suggests to me that he may be worth a shot in the rotation, but none of the current Astros starters are warranting the boot at this point. Regardless of what role the Astros use him in, Wilton Lopez should be able to provide the Astros with quality pitching for the next five seasons, chiefly due to his excellent control of the fastball.