Second Half Breakouts for Fantasy Baseball - Nick Mariano's "My Guys"

Nick's second-half fantasy baseball breakouts for 2025. These are all MLB hitters and pitchers he's trying to get on his rosters via waiver wire or trade including...

Congratulations to those of you who have built stellar foundations through the first half of the season, but what now? Seasoned veterans of the game know that no lead is safe, and we have to consistently improve our rosters to finish the marathon strong. Let's look at some players who I think could be pivotal for the stretch run.

I aim to focus on players who aren't rostered in every single league already, or if they are, then they probably aren't properly beloved by their fantasy manager. This list of "my guys" represents players I'm holding through rough patches or trying to add and buy (relatively) low where possible. These six players are primed for an exciting second half.

"My guys" for the second half of the fantasy baseball season tend to be undervalued or overlooked younger players. It may not all work out, but the ceilings available to us through them could win a league or two! Won't you join me?

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Jac Caglianone, 1B/OF - Kansas City Royals

This top prospect is battling Lady Luck at the dish, posting a horrid .140/.196/.264 triple slash in 138 plate appearances for a 22 wRC+ figure. And things are not getting better, as he’s gone 5-for-70 (.071) since June 21.

This is a strange sight after he posted a .322/.389/.593 slash line with 15 home runs in the minors, with six HRs in 12 flashy Triple-A games that led to his promotion. Heck, he’s even played a healthy right field for the Royals.

But hope springs eternal, and there’s far more brewing underneath the surface. If you need immediate hope, he posted four barrels with eight hard-hit balls in his final five games of the first half after just seven barrels over his first 30 contests.

The 6.1 degree launch angle is crushing his potential, but that sat at a flat 3.0 degrees and is now 12.8 degrees in 11 July tilts. His 11.1% Pull AIR rate ranks 307th out of 363 bats with 100 PAs since June began, and the 48.5% overall AIR rate is 313th.

But in that same timeframe, let’s look at these xStats when it comes to competitive swings. No other hitter has a worse gap between their expected slugging percentage and actual SLG, with 223 points separating his .532 xSLG and .309 SLG.

The 131-point gap between his .295 xBA and .164 AVG is 51 points higher than the next “unluckiest” player. (Including non-competitive swings makes it a 198-point SLG gap and 119-point BA gap, still squarely the worst.)

Let’s mix in that he is one of six guys with a bat speed above 77 mph since June 1 as well, joining Aaron Judge, Kyle Schwarber, Vladimir Guerrero Jr., Junior Caminero, and Jo Adell. So much about his game and past performance screams “star,” so let’s hope that soon we look back on the .147 BABIP and laugh.

Colt Keith, 1B/2B/3B - Detroit Tigers

The 23-year-old got off to a slow start, hitting .181 with only three extra-base hits in April before finding a groove in May. After thumping four round-trippers between April 30-May 8, murmurs that the prospect was finding his power stroke grew.

But the embers didn’t catch flame, with Keith going homerless between May 9 and June 19. Still, a rising fly ball rate has yielded four doubles and a pair of homers in 11 July games, which already tops his XBH tally of five from June.

I realize that his "breakout" has already begun, but I truly think that without a viable power surge that his fantasy perception is capped as an empty batting average. It’s easy to forget that he crushed 27 HRs with a .306 average between Double-A and Triple-A in 2023 at 21 years old.

And now his .540 xSLG since June began is tied with Brandon Lowe, with only eight other bats holding an xBA above .300 to go with it. He’s talented, Detroit is a growing offense, and perhaps this time the fire can stay lit!

Colt Keith since May 31:

.319/.379/.516, 150 wRC+, 15.5 K%, 8.7 BB%

Reminder he's still just 23 years old and played just 239 minor league games. Really think it's all starting to come together for the talented hitter. pic.twitter.com/TMDXtfhcUH

— Aram Leighton (@AramLeighton8) July 8, 2025

Luis Robert Jr., OF - Chicago White Sox

You simply cannot convince me that this man simply forgot how to play baseball. Going to a competitive scene with different coaches and a team that inspires with a higher standard should resuscitate things.

Luis Robert Jr. Drawing Recent Interest From Eight Teams https://t.co/LIsIwSWBFx

— RotoBaller MLB (@RotoBallerMLB) July 14, 2025

Robert still holds a top-20 max exit velocity on the year (115.8 mph, his fastest since 2022), a 90th percentile sprint speed (29.0 ft/sec), and plays strong defense with a plus arm. He turns 28 in August and is two seasons removed from an elite 38 HR, 20 SB campaign, with health the frequent worry rather than talent.

He’s walking more than ever and has actually dropped his swinging-strike rate by a percentage point for the second straight year. However, a career-worst HR/FB rate (11.4%) and a .250 BABIP that is 50 points lower than any other seasonal mark and 69 below his career rate (not nice) are crushing him.

*Also, teammate Kyle Teel has a 166-point gap between the .456 xSLG and .290 SLG. Another underperforming prospect that could step it up as time goes on.

Joe Boyle, SP - Tampa Bay Rays

Boyle had an ugly final appearance of the first half as the “follower” bulk arm behind Drew Rasmussen on July 11 at Fenway, but don’t let that distract you from the greater body of work.

The 25-year-old made waves with five innings of no-hit ball in a spot start on April 13 before returning to the minors for about three months, where he’s destroyed with a 1.85 ERA/0.99 WHIP and a 96:31 K:BB in 73 innings.

They’ve streamlined his approach and taken the ghastly walk rates that had flirted with 20% as a Red and Athletic and cut them in half. That's great, but there's another hurdle we have to deal with first.

According to Kevin Cash, Rasmussen will go back to full starts. So why is Boyle still here? Well, I think they move an arm like Zack Littell (or Taj Bradley?) to free up a full-fledged rotation spot where Boyle can get in a rhythm.

Kevin Cash just confirmed the #Rays rotation coming out of the All-Star break: Taj Bradley, Zack Littell, Ryan Pepiot, Shane Baz and Drew Rasmussen, with Rass expected to return to a five-inning workload.

— Ryan Bass (@Ry_Bass) July 12, 2025

Bubba Chandler, SP - Pittsburgh Pirates

It’s post-hype sleeper central here after so much early momentum and daily social media barrages on Pittsburgh posts to call the top prospect up were followed by a loss of control. But he’s found the zone again in back-to-back outings and should get a chance to shine shortly!

Each of his last two starts has gone for six scoreless innings, allowing five hits and two walks while striking out six against Cincinnati’s affiliate and seven against Atlanta’s. Those are the first outings to reach six innings since May 24, and more importantly, Pittsburgh is likely aiming to trade Andrew Heaney, Mitch Keller, and/or Bailey Falter by month’s end.

Grant Taylor, RP - Chicago White Sox

It’s tough to remember that Taylor required Tommy John surgery before his last season at LSU (where he was slated to pitch ahead of the recently-transferred Paul Skenes!). But what better way to move on than by emerging as a stud reliever able to hit 101 mph?

The 2023 second-round pick blew away Double-A hitters, posting a 1.01 ERA and 0.86 WHIP with 37 strikeouts over 26 ⅔ IP on the farm. He’s netted three saves and five holds in early action in the bigs,

Since Taylor was called up on June 10, only 12 pitchers out of 278 with at least five relief innings in that timespan have bested his 1.49 FIP. You wouldn’t guess that by his 4.41 ERA (none of the 12 have ERAs above 2.20), but here we are!

The flamethrowing right-hander is still ironing things out, and I know he’s allowed a run in three of his last five games while playing for a team that supplies few save opportunities! But the arsenal and general script here echo that of Mason Miller’s arrival for the A’s.

Grant Taylor (@whitesox No. 6) shows off electric stuff in his MLB debut:

⚫️3 up, 3 down
⚪️12 pitches, 10 for strikes
⚫️First pitch at 101.5 mph, 6 fastballs over 100 pic.twitter.com/1P2RpwexAJ

— MLB Pipeline (@MLBPipeline) June 11, 2025

Unlike Miller’s early form, Taylor has only walked four batters in 16 ⅓ IP. Despite that, untimely hits have found gaps for a dismal 55.6% strand rate. And he’s not getting beamed either, with one barrel allowed.

I recognize that being in a timeshare on the White Sox is suboptimal. But the lack of competition around him should keep him in the closing conversation even if a sustained stretch of bad luck hits. Plus, Dan Palyo took my favorite RP add in Ronny Henriquez in his second-half breakouts piece, so here we are with the runner-up!

Bonus: Max Muncy, 2B/3B/SS - Athletics

Muncy the Younger has an underwhelming .659 OPS with nine homers in 203 PAs, but had gone yard four times on six barrels in July. Still 22 years old, Muncy is growing into his 50-grade power tool at hitter-friendly Sutter Health Park.

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