Champ or Chump: Jake Mangum and Kyle Stowers Fantasy Baseball Outlooks

July 22, 2025

Are Jake Mangum and Kyle Stowers fantasy baseball sleepers, busts, or neither? Rick takes a deep dive into their 2025 fantasy baseball value.

Fantasy managers care about prospect pedigree when evaluating young players, and many top prospects go on to have great careers. However, we have to remember that pedigree is not essential for fantasy production. Whit Merrifield was never a huge prospect and still put up quality fantasy seasons. Such players are even more undervalued if they play in smaller markets.

Today's column is sponsored by Florida. Jake Mangum is a 29-year-old rookie, but he has an extensive MiLB track record that suggests he should keep doing what he's been doing. Kyle Stowers may have surprised some with his inclusion on the All-Star roster, but he wasn't selected just because the Marlins needed a representative. He's legitimately breaking out.

Here's a closer look at what these two outfielders can offer in fantasy for the second half.

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Jake Mangum (OF, Tampa Bay Rays)

7% Rostered

Mangum isn't a household name, but he's hitting .301/.342/.381 with two homers and 14 steals across 241 plate appearances (PAs) this season. Drafted by the Mets in the fourth round in 2019, he received a paltry $20,000 signing bonus and served as the player to be named later in two small trades. To say he wasn't a prospect is an understatement.

That said, his production translates well to 5x5 formats. Mangum has plus wheels with a Statcast Sprint Speed of 28.9 ft./sec, and his success rate of 82 percent will give him the green light on an analytical team like the Rays. We can expect a 30 SB pace the rest of the way, which can be difficult to find on waivers this late into the year.

Mangum's average should help too. He doesn't walk with a 5.4 percent BB%, and he's not going to start with his horrific 42 percent chase rate. However, he never strikes out either with a 12.9 percent K% backed by an extremely aggressive 61.6 percent Swing%. That means his BABIP determines his value, and Mangum's is a healthy .342.

Mangum doesn't hit many flies with a 22.1 percent FB%, so his speed lets him turn mediocre contact into base hits. Such a low FB% caps his power upside, but his 4.7 percent HR/FB suggests he doesn't have power upside anyway. Mangum slaps and dashes, and it's working so far.

Fantasy managers are skeptical if his roster rate is any indication, but Mangum's extensive MiLB resume supports this level of play. He cracked the High Minors in the Mets organization, slashing .294/.342/.459 with seven homers and 14 steals (70 percent success rate) over 330 PAs for Double-A (Binghamton) in 2021. He didn't walk (4.8 percent BB%) or K (17.6 percent K%) and posted a .340 BABIP.

Mangum returned to Binghamton in 2022 and hit .273/.338/.399 with two homers and seven steals in 158 PAs. His plate discipline didn't quite follow his career norms with a 7.6 percent BB% and 21.5 percent K%, but that's probably a small sample fluke. He still ran a .346 BABIP and was successful on 78 percent of his steal attempts.

The performance earned Mangum a promotion to Triple-A (Syracuse), where he hit .333/.365/.471 with two homers and seven steals over 148 PAs. His 4.7 percent BB%, 15.5 percent K%, and .383 BABIP were all in line with his previous work, and he was successful on 88 percent of his SB attempts.

Mangum was traded to Miami with Franklin Sanchez as a player to be named later in the deal that brought Elieser Hernandez and Jeff Brigham to the Mets (what a blockbuster), and the Marlins assigned him to Triple-A (Jacksonville) for 2023.

He hit .298/.346/.425 with five homers and 16 steals over 515 PAs, and you won't be surprised to learn that he didn't walk (5.4 percent BB%) or strikeout (17.7 percent K%) while running a .356 BABIP. He wasn't quite as efficient on the bases with a 73 percent success rate, but he wasn't horrible in that regard.

Mangum was traded to Tampa Bay in another blockbuster involving Calvin Faucher and Vidal Brujan going to Miami, while Mangum (as a player to be named later), Erick Lara, and Andrew Lindsey headed to the Rays. The Rays assigned him to Triple-A (Durham) to begin the 2025 campaign.

He hit .317/.357/.442 with six homers and 20 steals over 428 PAs. His plate discipline was virtually unchanged with a 5.4 percent BB% against a 17.1 percent K%, his .373 BABIP was high, and his 71 percent success rate on SB attempts was passable.

Altogether, we have over 1,500 PAs of MiLB data, suggesting that Mangum will hit for a high average and steal some bases with minimal power. You may not have heard of him, but there's an established track record here. He hit in the heart of Tampa's order while Brandon Lowe was on the injured list, but figures to hit sixth or seventh with the team fully healthy.

Mangum isn't exciting, but he's a good bet to help with average and steals. If you need help in those categories, this Champ is probably available to you. Just don't expect any power.

Kyle Stowers (OF, Miami Marlins)

74% Rostered

Many dismissed Stowers as the All-Star every team needs to have, but he's slashing .295/.372/.559 with 21 HR and four steals in 359 PAs with a blood-red Statcast page:

The Marlins acquired him with Connor Norby in the Trevor Rogers deal, and this season represents roughly half of his MLB career to date. Stowers made his MLB debut with the Orioles in 2022, so the 27-year-old has been around for a while. He just didn't do anything of fantasy note until this season.

Stowers didn't improve in a couple of areas: literally everything in his profile is better this season. His 10 percent BB% and 27.9 percent K% don't look great on the surface, but they're substantially better than his career marks of 8.2 percent and 30.8 percent, respectively. Furthermore, his 31.2 percent chase rate and 16.7 percent swinging strike percentage (SwStr%) are both career bests.

Stowers's HR/FB has tripled from 7.7 percent last season to 24.7 percent this year, and it's supported by everything that can support it. He's pulling more flies (10.3 percent to 28.2 percent). His average airborne exit velocity is up (94.6 mph to 96.2). His rate of barrels per batted ball event (Brls/BBE) has improved (10.9 percent to 19.6 percent). His Max EV is up (109.7 mph to 113.7).

Better yet, Stowers combines his newfound contact quality with more fly balls, bumping last year's 32.8 percent to 39 percent. Some players struggle with pop-ups when they increase their FB%, but Stowers has cut his in-field fly ball percentage (IFFB%) from 12.8 percent to 3.5 percent. It's amazing that he's improved everything all at once.

Stowers's .365 BABIP is a little inflated, but his .284 xBA and 22 percent LD% suggest that he still deserves a high average. His .570 xSLG is higher than his actual slugging percentage, creating an argument that he's been slightly unlucky to date.

We have to get really nitpicky to find flaws in Stowers this year. The lefty doesn't have a homer in 78 PAs against lefties this year, but his .294 average and .372 on-base percentage (OBP) suggest he's far from overmatched against southpaws. Miami is only hitting him fifth, but surely they'll give their best hitter a better lineup slot soon. That could give him further counting stat upside.

Stowers should be rostered in a lot more than 74 percent of leagues. The power is real, the average and OBP are plus, and he even made an appearance in the All-Star Game's first swing-off. Stowers was only an injury fill-in for Eugenio Suarez, but he still got a primetime appearance when the baseball world was watching.

Why don't I play in any leagues where Champs like this are still available on waivers?

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