Fantasy Baseball: 3 Things We Learned in Week 8

After a slow April, Dansby Swanson has really turned things around in the month of May. Who are some other players to keep an eye on?

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 eighth scoring period of the fantasy baseball season.

Ugly Duckling or Beautiful Swan(son)?

As the calendar flipped from April to May, Atlanta Braves shortstop Dansby Swanson was staring at quite an ugly start to the season. On May 1, Swanson's triple slash line was .189/.267/.316 with a mere two home runs, seven RBI, and one stolen base. After a semi-breakout in 2020 with a .274./.345/.464 line and 10 home runs in 60 games, there were fears that Swanson was in the midst of a major regression.

It turns out it was much ado about nothing.

In the month of May, Swanson has completely flipped the script with a .295/.329/.603 line to go along with 6 home runs and 12 RBI. In fact, his slugging and ISO are both top-20 among all Major League batters this month, joining teammates Freddie Freeman, Ronald Acuna, and another one we will get to below.

The cause for the improvement in Swanson's performance? Part of it is just positive regression. His batting average on balls in play (BABIP) in April was .258 but jumped up to .362 so far in May. But primarily he has just done what hitters are supposed to do: hit the ball hard.

Through April his barrel rate ranked 98th in the majors at just 7.8%. But in May, he has jumped to 40th overall, pushing hit above 13%. Swanson also started pulling the ball a lot more, so the combination of harder hits to one of the most advantageous parts of Truist Park (the third-best park for right-handed batters over the last three years) has an ugly start almost completely turned around.

Swanson remains rostered in only 76% of Yahoo leagues, so it's worth checking your waiver wire to see if a frustrated owner dropped him in the midst of his horrible first month.

Austin Riley on Fire

Also on fire in the suddenly explosive Braves lineup is another slow starter, Austin Riley. And for as hot as Dansby Swanson has been over the last month, it's safe to assume Riley has been even better over his last 10 games or so.

Among all Major League batters, Riley has seen the ninth-largest increase in his expected weighted on-base average (xwOBA) in his last 50 plate appearances, based on data from Baseball Savant.

According to Fangraphs, no batter has a higher barrel rate over the last 14 days than Riley (33.3%). Considering his seasonal number sits around 12.5%, it's no surprise that Riley entered into a power surge about two weeks ago from which he is yet to emerge. Riley's 7 doubles, 6 home runs, and 13 RBI in that span all rank top six among all hitters, clearly in an attempt to thank his fantasy managers for being patient through a slow start to the season.

Coming into the season, Riley was somewhat of a late-round sleeper considering he was drafted 215th overall on average and was the 62nd outfielder off the board according to FantasyPros' average draft position data. Just the last few weeks have been enough to turn a profit on that amount of draft capital, but now that he has moved to the middle third of the batting order (fifth and sixth in the Braves' most recent games), he should have even more opportunity for massive fantasy production with table setters like Acuna, Freeman and Marcell Ozuna in front of him.

The buy-low window is clearly shut on Riley at this point, but if you have an attractive opportunity to acquire the young outfielder -- especially in any kind of keeper format -- he is worth slightly overpaying for.

Add Casey Mize

Casey Mize (44% rostered in Yahoo leagues) - After scuffling through three of his first four Major League appearances, Mize is now on a streak of five consecutive quality starts, picking up two wins along the way despite playing with one of the worst offenses in baseball.

Mize has always had the pedigree to become a future ace, as he was MLB's fifth-ranked prospect entering 2020 and was drafted first overall out of Auburn in the summer of 2018. He is certainly already paying dividends for the Detroit Tigers, but is it sustainable? And what is in Mize's arsenal that has helped achieve his recent string of success?

The first thing that stands out about Mize is his devastating split-finger fastball. According to Baseball Savant, it is a pitch only thrown by 16 MLB starters with any consistency, and Mize's is the seventh-fastest at 87.1 MPH. Opponents are only slugging .382 against the pitch this year, mostly due to movement that is unlike any other pitch most batters have seen. Mize's splitter has the most vertical movement versus the average pitch of any starter this year -- even greater than established split-finger masters like Nathan Eovaldi and Kenta Maeda.

Mize features five different pitches in his arsenal, throwing none of them more than 26.9% of the time. That diverse set of pitches is enough to keep batters off-balance, but he tends to save his best stuff for when the count is in his favor. This display below from Baseball Savant shows which pitch Mize throws in each count, with the green/turquoise color being the splitter.

As you can see, he throws this pitch much more when the count is in his favor (0-2, 1-2, 2-2). And with its above-average movement in on right-handers and massive drop away from all batters, it is quickly becoming one of baseball's wipeout pitches.

If you are in a wins league, Mize gets bumped down a few notches because of the poor run support, but you are in need of elite ratios or quality starts, Mize looks like a keeper for the rest of the season.