Advanced MLB DFS Strategy: Targeting Bad Bullpens

With Opening Day of the MLB season only a little over a week away, it's time to start getting your mind right and preparing for a full season of MLB DFS action. Last summer we missed out on several months of MLB games due to the COVID pandemic, but we are going to get 6 months worth of DFS and for those of you who love to grind, I will be here all Spring, Summer, and Fall grinding with you and anchoring our MLB DFS premium coverage here at RotoBaller.

In this series of articles, I am going to try to lay out a number of overlooked factors that can be exploited by savvy MLB DFS players. Baseball is such a stat-nerd sport, and there are so many different statistics that one can consider when trying to break down any slate of games. I'll cover the basics for both hitters and pitchers in my annual DFS Strategy guide, but for today I want to focus on an often under-analyzed angle - and that's bullpens.

These days the vast majority of starting pitchers aren't pitching all that deep into games. When the starting pitchers are announced each day, we often look at who the weakest starters are to see who we want to stack against. But far too often we don't consider that at least that the hitters we roster will be facing the opposing team's bullpen for at least a third of their at-bats, or more if we think they chase the starter early.

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Targeting a weak, or even a mediocre pitcher that has a bad bullpen behind them is one way to win a GPP. If an offense explodes for double-digit runs, it's usually not all done just against the starter. When offenses are pouring it on, they're often beating up on the long relievers and many teams with poor starting pitching also end up with overworked bullpens as a result. It's a shrewd move to consider bullpens in addition to starting pitchers when selecting those offenses we want to stack.

Here's a look at the bottom half of the league in innings pitched by their starters.

2020 was a unique season in that some teams piggybacked starters, and the trend of using openers instead of traditional starters, popularized by Tampa Bay (whose starters threw the fifth-fewest innings last year, but were incredibly effective with the fourth-best xFIP) might skew our data here a little. It's still a good place to start if we are trying to identify teams that had overworked or overused bullpens. The Dodgers and Mets show up on this list, but both teams were top-ten in xFIP and have quality starting pitching and L.A. has been taking the approach of managing their starting pitchers' workloads throughout the season.

2020 Bullpen Stats: xFIP

Looking at ERA isn't usually a good idea and I'll spare you the time getting into why there are better performance indicators for pitchers. Using FanGraphs, let's just take a look at last year's bullpen stats here sorted by the worst xFIP (expected fielding-independent pitching), which I view as a solid stat that encompasses the overall effectiveness of pitchers.

We see four teams with bullpen xFIPs up over five, with Seattle being considerably worse than the rest of the field. The Mariners were a bullpen I picked on quite often last season and they are going to show up near the top of all these statistics that I am going to highlight here.

Despite having pitcher-friendly home ballparks, Miami and San Francisco relievers were bad last year, too. I'm not surprised to see Colorado and Texas in the top five, as those have been two of the most hitter-friendly environments. The Nationals bullpen was horrendous in 2019 and was slightly better last year, but still bad enough to crack the top-10.

2020 Bullpen Stats: BB/9

I love targeting pitchers who walk too many hitters. Walks put men on base and increase the chances for big innings. A lot of relief pitchers carry high walk rates when compared to starters which is likely due to having to pitch in more high-leverage situations. But what we are looking for here is bullpens that are consistently walking more batters than others and once again we see Seattle at the top of the list.

Seattle's number of walks is even more concerning when you pair it with their lack of strikeouts. A bullpen that has a K/9 rate of fewer than 9 means they aren't even striking out a hitter per inning. Strikeouts get you out of jams, even if you are putting baserunners on with walks, which helps explain why a team like the Cubs with a high K/9 (10.66) can withstand their high walk rate (4.66 BB/9).

2020 Bullpen Stats: HR/9

Home runs are king in DFS. If you find the right stack of hitters that can produce multiple dingers or locate a double-dong or two in your lineup, you're well on your way to cashing, and in contention to take down a tournament. Most relief pitchers are hard throwers these days and give up a lot of long balls. Here's a look at the worst bullpens sorted by their HR/9.

The Phillies pen gave up a dinger every four and a half innings and so it's no surprise that their HR/FB ratio was over 20%. There are our lowly Mariners again with the second-worst mark (albeit a distant second) and some of the same bad bullpens we've seen in the other data (COL, MIA, WAS...)

Summary

1. We are going to need a few weeks of data once the season starts to get any kind of idea as to the quality of each team's bullpen, but once we have a decent sample this is data that you should be considering when doing your daily DFS research.
2. Just because a bullpen rates poorly statistically, it doesn't mean we should target them no matter what. If they have a quality starter out there that we don't want to target, we shouldn't stack against that starter with the hopes they get pulled early.
3. If we want to target a bad starter with a good bullpen, we should probably think twice. If you don't get the production you're looking for from your hitters the first two times through the order, you might be in trouble as your hitters end up facing better pitchers the second half of the game.
4. The perfect situation that we are looking for is a poor or mediocre starter who is also backed by a poor or mediocre bullpen. Then we can stack hitters with confidence, knowing that they'll have 4-5 at-bats against hittable pitchers regardless of how long the starting pitcher lasts out there.

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