Managing a fantasy baseball team is all about informed decisions. Sure, the occasional gut call can be fun to make, but it's best to rely on data in order to increase one's chances of making the proper move.
There's a bevy of stats out there, but most of what you'll find is more descriptive than predictive. We're adept at explaining why something happened, but forecasting what will happen is still a work in progress.
With about one month left in the fantasy baseball season, every move is magnified since there is less margin for error. The problem is, some of the season-long information that we've been relying upon to help make decisions up until now is no longer reflecting the true picture of things. With so many MLB rosters having been altered at the trade deadline (not to mention the promotion of several top prospects), stats which painted a reliable picture of things through the end of August may no longer represent reality.
What follows is a review of some of the common matchup information fantasy managers use to evaluate their rosters, be it for pickups or player activation. The focus will be on scenarios that have changed the most since the trading deadline. The cause of the change won't always be roster-related as a one-month sample is naturally going to be influenced by variance. Sometimes, the quality of opposition over that span affects things. This is where speculation, and maybe a gut call is required.
Using the New York Yankees as an example, injuries have been a factor but, excluding Aaron Judge, their offense has been in a rut. The numbers say it's safe to stream pitchers against them. Does your gut agree, or is it concerned that the Yankees might "snap out of it" at any moment?
Lineups to target when streaming pitchers
There are two primary stat considerations when selecting a pitcher for a spot start: opponent wOBA and K%. Yes, BB% and HR% are also factors, but K% is paramount since it has a greater influence on scoring, be it in points formats or rotisserie-style leagues. The wOBA (weighted on base average) speaks to a lineup's run-scoring potential.
The handedness of the pitcher is a chief component of many decisions. Keep in mind that, regardless of the time frame, the numbers reflecting performance against right-handers have less variance than those against a southpaw since 72% of plate appearances occur with a righty on the hill. As such, especially in a one-month sample, data involving left-handed pitching is less reliable than the same time frame when it comes to right-handers.
Streaming LHP
Since the trade deadline, the Miami Marlins, New York Mets, Chicago Cubs, Detroit Tigers and Arizona Diamondbacks are the five worst teams in terms of wOBA with a left-hander on the hill. While the Marlins have been among the worst lineups all season, none of the other four had been clear lineups to target.
The Mets tried to address their production against lefties by trading for Darin Ruf. Since joining the club, Ruf has posted a dismal .167/.213/.238 line. Granted, his history suggests he can turn it around, but don't shy away from using left-handers against the Mets.
The Diamondbacks have promoted Corbin Carroll and given Jake McCarthy more playing time over 2022's second half. McCarthy has hit lefties well, but Carroll has struggled. Lefties Daulton Varsho and Alek Thomas comprise the rest of Arizona's outfield and designated hitter spots, so it's understandable why they're vulnerable with a lefty on the hill.
According to the recent numbers, it's also safe to start lefties against the Yankees, Cubs and Tigers. The Yankees' thought process has already been addressed. As for the Cubs and Tigers, for most of the season they were around the league average when facing left-handers, but lately their production has dropped. Both clubs are auditioning players for next season, so there is more than simply variance in play. As such, they can both be targets for a lefty starter.
In terms of strikeouts, the Marlins, Pittsburgh Pirates and Milwaukee Brewers remain the optimal lineups to pick on when desiring whiffs from a lefty. Since the trade deadline, the Kansas City Royals, Washington Nationals, Boston Red Sox and Minnesota Twins have all fanned at an elevated clip against left-handers. The Royals are looking at several youngsters, so their increase is more than variance. The Nationals dealt Juan Soto and Josh Bell, hence it makes sense their punch-out total has increased. Injuries have beset the Twins and Red Sox, so there's more speculation involved when figuring out what to do with those teams going forward.
Streaming RHP
The Tigers, Oakland Athletics and Pirates have been the top three targets for righties all year. Even though the first two have shown recent improvements, it's not nearly enough to stop picking on their lineups when selecting your streamers.
Relative to their season-long numbers, the Yankees, Cleveland Guardians and Marlins have struggled the most against right-handers since the trade deadline. It's already been established that it's risky to target the Yankees, and the Marlins are very much still ripe for the picking. The Guardians? Well, they're quite the conundrum. Peaking at the strikeout data reveals they remain one of the toughest lineups to send back to the dugout, bat in hand. As such, if strikeouts are part of your league's scoring algebra, there are better lineups to target than Cleveland.
There isn't much else to glean from the strikeout data as the two offenses with the biggest increase are the Tigers and Yankees. Streaming against the Tigers is nothing new, while (not to sound like a broken record) doing so against the Yankees remains a risk.
Lineups to avoid when streaming pitchers
Streaming LHP
Both the St. Louis Cardinals and Atlanta Braves have crushed southpaws all season and continue to mash, hitting them even harder since the deadline. While you probably know you shouldn't go anywhere near these teams, there are a few other places not to look when you want to sneak in a spot-starter or two.
We're talking about the Baltimore Orioles and Royals, both of which have moved from around league average in wOBA against lefties to being one of the better lineups over the past month. With the Orioles, while they recently promoted Gunnar Henderson and acquired Jesus Aguilar, their improvement is a combination of variance and a young lineup continuing to get better. They're now a scary lineup to target with a lefty.
As mentioned earlier, the Royals are looking at some young players who are fanning at an elevated clip, but in spite of the swing-and-miss, they've also produced quite nicely in this span. It comes down to your league's scoring and team needs. If strikeouts are more important to your pitching stats than either run or hit prevention, pick on the Royals. Otherwise, steer clear as they are now a legit threat to your ratios.
The Chicago White Sox, Texas Rangers and Braves have all whiffed less often as of late. Then again, none of these teams had been striking out at a high rate all season anyway. There aren't any unexpected teams to avoid when pining for left-handed K counts.
Streaming RHP
Earlier, we noted the left-handed lean of the Diamondbacks outfield. While they are struggling against southpaws, those Arizona youngsters are thriving with the platoon edge. For much of the campaign, this lineup was around the league average with a right-hander on the hill but, for the past month, they've been one of the most productive units. Be wary of using a righty against the Diamondbacks.
For much of the season, a sneaky play was using RHP against the Tampa Bay Rays so that you could watch your strikeout total soar. Lately, it's been a different story as the Rays are getting healthy. That means they're able to revert to using more platoons, thereby reducing strikeouts. If you've been benefiting from targeting the fact that Tampa Bay's lineup had been fanning at an uncharacteristically high clip, it's time to look elsewhere.
Stolen bases
While steals may seem more important in rotisserie or category-based scoring, unearthing players with a chance to get on, steal a base, and then score can absolutely fortify a lineup using points scoring. While trusting season-long data doesn't account for changes behind the plate, a one-month sample can be biased due to the ability of the opposition to swipe bases. The batteries with the biggest changes will be presented. In come cases, there is a clear change in backstops. Other times, a gut call is in order.
Batteries to target
For the season, the San Diego Padres, Los Angeles Angels, Braves, Rangers and Colorado Rockies have been the most vulnerable in terms of yielding steals. Four of these clubs are still easy targets, but the Rangers have been doing a better job over the last month. Their catching rotation hasn't changed, but not only has the Rangers pitching improved, but they're also working in new arms. Perhaps the drop in stolen base success is more about an improvement in holding on runners. That said, the success rate is still 70%, only a tick better than average, so while the Texas battery shouldn't be targeted, it also shouldn't be shunned for established pilferers.
A pair of AL East teams have moved from nabbing an above-average number of would-be base stealers to below average. Perhaps it's from facing common opponents since the trade deadline, but the Orioles and Toronto Blue Jays are suddenly less proficient at throwing out runners. They're not in target range, per se, but they should not be avoided either.
Batteries to avoid
The Yankees, Philadelphia Phillies and Tigers are the three teams that have thrown out the highest percent of runners for the season. While the Tigers have fallen back a little over the last month, the Yankees and Phillies have gotten even better, so definitely avoid those clubs.
Four teams exhibiting a huge improvement in controlling the running game (after having being around average) are the Royals, Rays, Seattle Mariners and Cubs. None of them acquired a new catcher, but the playing time within their catching corps has shifted. Stolen base specialists should be started regardless, but if you're deciding between two players, one of which counts steals among his primary production, the sage play is to avoid the backstops from this quartet of defenses.
A word about bullpens
An important, but often overlooked aspect of making roster moves is accounting for bullpens. It's a slippery slope, since the low number of reliever innings is subject to huge variance, but often changes can be attributed to the shuffling of the bullpen constituents. Again, the relevant raw data will be presented. Some repercussions can be explained objectively, while others require subjective narrative.
Bullpens on the rise
The Guardians, Cincinnati Reds, Seattle Mariners and Angels have improved the most since the trade deadline. Cleveland and Seattle relievers were already solid, so there's nothing actionable here. However, the Reds and Angels both have starting pitchers that are often targeted either to fortify a traditional fantasy lineup or with a DFS stack. Mistake? Bullpens also have betting implications when gambling on "results through five innings" compared to the whole game. If you have been assuming that hitters would take advantage of a subpar Angels or Reds bullpen, it's time to re-evaluate.
Bullpens on the decline
The relievers exhibiting the biggest jump in ERA are those from the Tigers, Diamondbacks, Red Sox and Cubs. All but the Red Sox traded away solid hurlers -- Boston has been terrible all season, but is even worse with Tanner Houck. The scenario most relevant to roster decisions is in Motown since their bullpen was solid for most of the season. However, dealing away Michael Fulmer changed the dynamic even more than simply losing his arm as the others have struggled in their new roles. If you had been avoiding using hitters because they would have to face a good Tigers relief unit, that's no longer a concern.
As you continue your final march towards a potential title, keep these stats in mind and monitor them for changes. Good luck to you all down the stretch -- although, if you stay diligent, you won't need luck.