There were a million question marks throughout the offseason as Ben Cherington and the Red Sox put together the current starting rotation. Many saw it as a "gum and duct tape" unit pieced together with subpar players that was missing at least one key piece. So far, those people have been right. That’s not really what I want to talk about today, though.
One thing that was abundantly clear when this rotation became fully formed was the emphasis the front office was putting on ground balls. With each new addition came another pitcher who induce ground balls more often than not. It’s not the only way to limit damage, of course, but it’s a sound strategy in a vacuum. We’re now 31 games into the season. Has the ground ball strategy been working out?
Looking at the early season numbers, things haven’t exactly gone according the plan. The entire staff’s (including bullpen) ground ball rate is sitting at just 45.3 percent, putting them right at the middle of the pack at 16th in the league. Most of the ground ball emphasis was placed in the rotation, though, and things look a little better there. The starters have a collective 47.5 percent ground ball rate, ranking 11th in baseball. They’re in the top half of the league, which is nice, but it’s a bit underwhelming considering the expectations coming into the year.
So, has it been just one or two pitchers regressing heavily, or is it more of a team-wide ailment? Of the pitchers with at least ten innings under their belt, Justin Masterson, Clay Buchholz and Edward Mujica have induced grounders at the best rate, and are the only three above 50 percent. That clearly shows inducing ground balls isn't a sure-fire path to success, but that doesn't mean it can't help. Besides Masterson and Buchholz, the other three members of the rotation have watched their numbers fall rather precipitously.
Miley has been extremely disappointing this season to the point where there isn't just one thing that has caused his struggles. With that being said, it’s safe to say a relative lack of grounders has hurt. In the last two years, the former Diamondback had ground ball rates of 52 and 51.1 percent, respectively. This year, that number has tumbled all the way down to 45.2 percent. essentially league-average for a starting pitcher.
Looking at his zone profile, he’s been pounding the lower part of the zone on his arm-side. The problem, however, is that these balls aren’t being hit on the ground. As you can see, most of his pitches last season were hit on the ground regardless of where it was thrown. The most concerning part of the 2015 plot, however, is the left side of the zone -- inside to righties and outside to lefties -- especially the lower part. If he’s going to improve, turning that section more red will go a long way.
None of the Red Sox starters were known for their ground ball prowess more than Porcello. His poor infield defense in Detroit foiled his ERA because of his ground ball contact oriented style. Well, this season, that lauded ground ball rate has fallen all the way down to 45.3 percent, far and away the lowest mark of his career.
That is a striking difference between 2014 and 2015 for Porcello. Last season, he pounded the bottom of the strike zone like he was Harold from Hey Arnold. This year, he just hasn’t been able to find that groove yet. He’s looked better in the last few outings, and considering his past, there’s reason for optimism for his ground ball rate.
Kelly came in to town before last offseason, so he kind of missed the ground ball hype train. That doesn’t mean he didn’t deserve to be mentioned, though. Coming into this season, he had never had a rate below 50 percent and he topped out at 55 percent in 2014. He’s fallen almost 11 percentage points from last season, though, coming in at 44.4 percent through his first six starts.
Kelly’s issues are a little more difficult to figure out. It’s been a little bit of everything, but the biggest thing that jumps out here is similar to Miley’s. He hasn’t been able to induce grounders on his arm-side like he used to. There’s clearly been a lot of issues in Kelly’s game this season, but allowing too many balls in the air has been a big one.
Part of me wonders if this was contributing factor in the firing of Juan Nieves. Both Kelly and Miley have struggled in the same area of the zone in ways that they never had before. Porcello and Kelly have both seen their strikeout rates grow significantly, but with it came much more hard contact, especially in the air. Nieves’ firing was surely more complicated than just one thing, and it’s impossible to know the real cause without being in the clubhouse. Three significant disappoints in an area that was supposed to be a huge strength doesn’t bode well for anyone, though. The good thing is it’s May 11, and there is plenty of time for the ground ball problem to rectify itself.
*Batted Ball Numbers are from Fangraphs. Zone Plots are from Brooks Baseball.