Four Rookies Who Surged In September - 2024 Fantasy Baseball Sleepers

February 7, 2024

Lauren looks at four MLB rookies who surged in September and may be fantasy baseball draft sleepers for the 2024 season. Keep these fantasy breakouts in mind.

In 2023, we saw the MLB debuts of several well-known fantasy baseball prospects, such as Jordan Lawlar, Grayson Rodriguez, AJ Smith-Shawver, Pete Crow-Armstrong, and Anthony Volpe. However, many more "under the radar" prospects produced quality rookie campaigns and surged in September as a potential preview of what is to come in 2024.

Rookie of the Year winners Gunnar Henderson and Corbin Carroll will undoubtedly be highly coveted in upcoming fantasy drafts, but what about the rest of those entering their sophomore campaigns? Which fantasy baseball sleepers should you consider for the 2024 fantasy baseball season? These names might not be the first off the board but that doesn't mean the talent and production isn't there; plus, they possess an average ADP of 87.6.

So when you're preparing to draft this year, keep an eye out for these names. They just may surprise you by being even better during their sophomore seasons.

Triston Casas, 1B, Boston Red Sox

The Red Sox have had trouble finding consistency at first base since 2018 World Series champion Mitch Moreland was traded to the Oakland Athletics in 2020. Luckily, they may have found their long-term answer in 2018 first-round draft pick Triston Casas. The 6-foot-4, 244-pound first baseman boasts immense power -- belting 24 home runs in 2023 -- and a keen eye at the plate, drawing 70 free passes last season.

Back-to-back games with a home run for Triston Casas. pic.twitter.com/ej0THAn0io

— Red Sox (@RedSox) July 15, 2023

After posting a .728 OPS and striking out 76 times across 291 plate appearances in the first half, Casas kicked it into gear in the second half. He batted .317 and had an OPS of 1.034 in 54 games, along with 15 home runs and 38 RBI. Not to mention the 24-year-old's Baseball Savant page is a sea of red, most notably ranking in the 93rd percentile in BB %, 92nd in xwOBA, 89th in xSLG, and 86th in Barrel%. Casas still struggles against lefties, but figures to be Boston's everyday first baseman.

Sure, he does have the benefit of his home field being Fenway Park, a stadium that loves left-handed power, but it's clear that the Red Sox have something in Casas. His .263/.367/.490 slash line and a strong finish to the season helped him to place third in the AL Rookie of the Year voting. RotoBaller ranks Casas as the 10th-best first baseman with an ADP of 105 and ATC projects him to hit 18 home runs in 2024.

Royce Lewis, 3B/SS, Minnesota Twins

The first overall pick in the 2017 draft, Royce Lewis has had somewhat of a tumultuous start to his major league career. He's dealt with a multitude of injuries that have limited him to just 70 games in two seasons.

He appeared in 58 games for the Twins last year and particularly thrived in September, slashing .313/.410/.612 with six home runs and 23 RBI. He also was a lone bright spot for Minnesota in the postseason, carrying them to a Wild Card series win against the Blue Jays with two home runs in Game 1, and adding two more during the ALDS vs. the Astros.

Royce Lewis hits the first home run of the #postseason! 💪 pic.twitter.com/oxer3l0tOH

— MLB (@MLB) October 3, 2023

As long as he can stay healthy, the 24-year-old should continue to do big things in the Twin Cities; RotoBaller surprisingly places him seventh among qualified third basemen and has an ADP of 50.5. He ranked in the top six percent of the league in max exit velocity and produced a .481 xSLG and .393 wOBA.

Lewis' plate discipline could use some improvement, with a 23.0 K% and 8.4 BB% in 2023, but he operates as a five-tool player. He may not be as speedy as he was before his two ACL tears, but it can still factor into his game.

Tanner Bibee, SP, Cleveland Guardians 

Cleveland's top pitching prospect Tanner Bibee made his debut in April of last year and helped to fortify a scuffling Guardians rotation. He settled for 5.2 innings of one-run ball and eight strikeouts against the Colorado Rockies in his first major league start.

The soon-to-be 25-year-old remained mostly consistent for Cleveland throughout the year, with one of his best months coming in September. He pitched to a 2.60 ERA in 17.1 innings across three starts, holding opponents to a .180/.239/.262 slash line with 16 strikeouts. It wasn't enough to help his team make the playoffs, but he left the Guardians feeling confident in his future in their rotation. He finished second in the AL Rookie of the Year voting.

Tanner Bibee made it look pretty effortless yesterday, striking out 7 including Shohei Ohtani twice.#ForTheLand pic.twitter.com/HsKCQJN4R5

— Cleveland Guardians (@CleGuardians) May 15, 2023

Overall, the former fifth-round pick finished his rookie campaign with a 2.98 ERA and 141 strikeouts in 142 innings of work. Despite a strong season, one cause for concern is Bibee's tendency to allow hard contact, allowing a 115.3 max exit velocity, which ranks in the bottom seven percent in the league. He could be a solid pickup in the middle rounds of fantasy drafts with an ADP of 118.

Kodai Senga, SP, New York Mets

Most major league players don't make their debuts at age 30, but that was the case for New York's Kodai Senga, who was posted by NPB's Fukuoka SoftBank Hawks in December 2022 and signed as a free agent with the Mets. He was named an All-Star in his first year in the bigs, and it was well deserved.

Kodai Senga and his feared ghost fork come in as our #2 NL rookie from the 2023 season! 👻 pic.twitter.com/g4NfXANAyd

— MLB Network (@MLBNetwork) January 28, 2024

The Japanese right hander at times grappled with his command -- as exemplified by his league-leading 14 wild pitches and 77 walks -- but he made up for it with a 2.98 ERA, 1.22 WHIP, and 202 strikeouts in 166.1 innings pitched. Senga was by far the most reliable arm in the Mets rotation, one that lost both Max Scherzer and Justin Verlander during the season.

His efforts found him in the top 10 in the NL Cy Young Award voting and placed second in the NL Rookie of the Year voting. Like Bibee, though, Senga was in the bottom seven percent of the league in max exit velocity, something he'll look to improve as he headlines the Amazins' starting five. His strikeout rate makes him a hot commodity in fantasy drafts, but it's possible his walks and .279 BABIP could catch up to his ERA and WHIP in 2024.

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