Fantasy Baseball: 3 Things We Learned in Week 10

Baseball fans love their stats. We devour them, dissect them, and build our fantasy rosters around them. Each week of the 2021 baseball season, we will be gifted with another statistical sample size of pitches, plate appearances, and playing time. Knowing it often takes hundreds or even thousands of pitches or batted-ball events for trends to normalize, how should fantasy managers adjust to the ebbs and flows of weekly player performance?

Each week during this season, this piece will look at trends that have emerged over the past week and determine if it is signal or noise moving forward. What is prescriptive in helping build winning fantasy teams and what can be ignored as small sample size noise? Hopefully, we can make sense of what has just happened to help us make smarter roster and free agent budget decisions.

Let's take a look at some of the data from the tenth scoring period of the fantasy baseball season.

Will the Real Cedric Mullins Please Stand Up?

Baltimore Orioles leadoff man Cedric Mullins has two competing trends recently that stand in stark contrast to one another. The first exists in his last five games where he has 12 hits, 3 home runs, 4 RBI, and 7 runs – raising his batting average 27 points to .322. The second comes in the 13-game, larger sample before those five games. In those contests, he had just 11 hits, no home runs, and 2 RBI while his batting average dropped 18 points. As with most debates in life, the real player is probably somewhere in the middle, but can we at least extract some meaning from the recent hot streak to see what to expect moving forward?

Looking at Mullins' year-over-year Statcast data changes in expected weighted on-base average (xwOBA), we see that he hovered around the .230-.260 range for the first three years, but that has exploded to .342 this year. That number represents the sixth-highest jump among all major league batters this year, but there are signs that it just might be warranted based on batted ball information we have through the first third of the season.

Literally every number you would want to use to measure the predictive nature of Mullin's strong season is going in the right direction. His average exit velocity, barrel percentage, walk rate, and in-zone contact rate are all up. His strikeout rate, swing and miss percentage, and out-of-zone swing percentage are all down. According to Fangraphs, his contact percentage is now top-25 in the league.

This looks like a player who is putting everything together in his age 26 season, just at the cusp of prime age for hitters. If you have a league manager who doesn't know what they may have with Mullins, who was drafted as the 126th outfielder overall, see what it might take to pry him away. With nine home runs and nine steals already, this could easily be a 25-25 season incoming.

Keeping an Eye on Dylan Bundy

Expected stats are having a moment right now with their usability and utility in question in terms of how predictive or prescriptive they might be in determining what a player may do for the last four months of the 2021 season. One player who would probably really like that debate to be settled is Dylan Bundy. Among all qualified starters in MLB this year, he likely has the best case to be made for results not keeping up with expectations.

Looking at the differences among all pitchers between ERA and expected ERA (xERA), wOBA and xwOBA, and slugging percentage (SLG) and xSLG, Bundy ranks top-15 in the largest gap in each of those categories. Stats like SLG and wOBA are not typically counted in fantasy leagues, but Bundy's ERA is where fantasy managers are really feeling it this year. His actual ERA (6.49) is 2.51 runs higher than his xERA (3.98), representing the largest spread among qualified starters this year.

What can be the reason for this discrepancy? The first thing we should always check with pitchers is batting average on balls in play (BABIP). Bundy's sits at .293, which is just barely above the league average this year (.286), so he is not getting unlucky there. His line drive/ground ball/fly ball splits are in line with his career averages. He is giving up the lowest amount of hard contact since his 2016 season. From what I can see, it really looks like it is coming down to one number that is biting Bundy in the backside this year.

Bundy's 20.3% HR/FB rate is far and away a career-worst and is 50% worse than the league average of 13.4% across major league baseball. According to Baseball Savant's park factors, Angels Stadium ranks second for highest home run rate this year, a full 43% above league average. This spike, along with Bundy's spike in home runs per fly ball, is out of whack with numbers from the past three to five years, so one has to think they will start to regress back to normal. This makes Bundy a strong buy-low candidate right now, especially as he enters his next two games against the Royals and Athletics in extreme pitchers' parks.

Add Eric Haase

Eric Haase (12% rostered in Yahoo leagues) - Similar to Mullins, Haase is on a monumental heater right now on a bad team, so even after Sunday waivers and FAB bids, Haase remains criminally under-rostered in many fantasy formats. In his past four starts, Haase is 7-for-15 with five home runs, seven RBI, and six runs. With three games on tap against the Seattle Mariners this week, you may want to jump now before your league mates grab the hottest catcher in the league.

Catcher has -- like every year -- been a wasteland this season. Of the top 10 catchers drafted in Yahoo leagues this year (not including Isiah Kiner-Falefa, who is a Yahoo cheat code), only five are top 10 in standard 5x5 leagues right now, while players like Buster Posey, Mike Zunino, and Carson Kelly have managed to find their way into the top 10. Anytime we get the opportunity for a catcher with a big bat, that should be a signal to jump, and we certainly have that with Haase.

As you can see in the graphs below from Baseball Savant, in his parts of four major league seasons, the 28-year-old Haase has drastically improved his barrel rate while also cutting the percentage of pitches he chases outside the zone from almost 50% to under 30%.

On a team headed nowhere like the Detroit Tigers, Haase is going to get a chance to play as much as he can. Now moved up to fifth in a typical Tigers batting lineup, Haase looks like a mid-season gem at an otherwise messy position.