Red Sox offense struggles against starting pitchers

This post is a response to a question received in our OTM Mailbag. Have a question? Hit us up at OTMMailbag@gmail.com.

Wanted to see if you guys could look into why the Red Sox offense struggles far more against opposing starting pitching and seem to have much better luck hitting relievers. I know generally speaking a SP is a pitcher of higher quality than RP, but it seems to be deeper than that to me. Could we be getting out game planned? Or maybe we just need a few turns at the plate to get comfortable? Or are we just due for some serious BABIP good karma with RISP.

-Drew from Louisiana

Ed. Note: The numbers below do not reflect the game played on Tuesday against Andrew Cashner and the Rangers.

We all know how frustrating the Red Sox offense has been, but this is an interesting question that brings in a perspective I hadn’t thought much about. Is the team struggling with starting pitchers more than they are with relievers?

The simple answer is yes, which we can find using Baseball-Reference’s Play Index. Against starting pitchers, the Red Sox are slashing .259/.321/.418 for an OPS of .739. Once a reliever comes into the game, the team is hitting .280/.362/.392 for an OPS of .754. So, just on a basic level the team is slightly better against relievers than they are against starters.

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The difference is actually more stark when you look at the numbers in context, though. While Drew points out that starting pitchers are generally more talented arms than their relieving counterparts, teams have more success at the plate against starters because they face them so many times. Especially in today’s game, it is just very difficult to have a ton of success against the ever-growing number of dominant relievers who only have to worry about throwing one inning at a time.

To put these numbers into some more context, the Red Sox are the 20th best hitting team, by OPS, when a starting pitcher is on the mound. On the other hand, once the other team has reached their bullpen, they are the sixth best hitting team, by OPS, in baseball. By my count, the Red Sox are one of just nine teams in the entire league who are better against relievers than starters in 2017.

This is a weird trend, and it’s worth digging a little bit deeper to see if we can find any causes. To see how much of this is based on sustainable numbers, let’s look at the Red Sox’ strikeout and walk rates against both starters and relievers. In the other column in the table below we can see how the league as a whole performs in those areas as well.

So, there’s a few things going on here. First of all, the Red Sox are at least average in terms of plate discipline against both starters and relievers. This alone doesn’t mean they are due for positive regression against starting pitchers, of course, but it’s a step in the right direction.

Now is the part where we get to the power, as that has been an overarching theme over the entire disappointing season for the lineup. This has continued to be the case regardless of which kind of pitcher they have faced. Against starters, the team has posted an Isolated Power of .161 compared to a mark of .112 against relievers. Note that essentially everyone hits for less power against relievers. In terms of rank, though, the Red Sox are actually worse in this area when the other team reaches into their bullpen. Boston’s offense ranks 28th in ISO against relievers while ranking 21st against starters.

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In the end, and perhaps boringly, this seems to come down to batting average on balls in play. Against starters, the Red Sox have a BABIP of .287, which is 19th in the league. Meanwhile, they’ve posted a .339 mark against relievers, which is second in all of baseball. Unfortunately, the Play Index tool doesn’t feature batted ball data to see just how much luck is involved with the disparity here, but one would think at least some regression is coming for both sides.

Before we leave here, I just wanted to note that a few players in particular stand out in this area, and I will highlight them below.

The bad news with all of this is that I’m not sure I can make a strong statement about what this means. It’s not that the Red Sox haven’t been able to get off to strong starts, because relative to the league they are worse in the middle innings than the beginning ones. The only piece of speculation that I have is that opponents are able to find holes in some players swings the second time they face them and Red Sox hitters haven’t been able to counter-adjust. It is also worth noting that, with the lack of offense against starters, the Red Sox have found themselves behind in the late innings more often. Because of this, they have probably seen a lower quality of reliever compared to some other teams around the league.

Either way, I thought this was an interesting way to look at the sputtering offense that I wouldn’t have thought of without Drew’s question. Since it’s a matter of BABIP, mostly, I would think that the Red Sox will start coming around against starters and performing a little worse against relievers, but it’s a strange trend that isn’t shared by a large chunk of the league. Specifically, look for the players in the chart above to see if their performances start to even out regardless of which kind of pitcher is on the mound.