3 Impact Fantasy Baseball Prospects To Stash - Coby Mayo, Hyeseong Kim, Gunnar Hoglund

Three top fantasy baseball prospects - Coby Mayo, Hyeseong Kim, Gunnar Hoglund - that can make big impacts. These MLB prospects are waiver wire pickups or stashes.

We are starting to see more prospects get called up by major league teams. Prospects like Chase Dollander, Nick Kurtz, Edgar Quero, and Hunter Dobbins have all been promoted over the past few weeks. As we head into Week 6 of the fantasy baseball season, more prospects should find their way on big league rosters.

Three prospects who have been called up recently are Baltimore Orioles third baseman Coby Mayo, Los Angeles Dodgers infielder Hyeseong Kim, and Athletics pitcher Gunnar Hoglund. All three players have the potential to be solid fantasy options in 2025.

So, should fantasy managers be adding Mayo, Kim, and Hoglund in fantasy leagues? Let's dive in and see if these three prospects should be grabbed off the waiver wire before it's too late.

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Coby Mayo, 1B/3B, Baltimore Orioles

Current Level: Baltimore Orioles
Availability: 11% rostered
2025 AAA stats: 28 G, .252/.346/.523, 6 HRs, 22 RBI, 16 BB, 1 SB

Since being drafted in the fourth round of the 2020 MLB Draft, Mayo has shown his potential throughout the minors. After delivering solid all-around numbers in 2021, the Orioles' top prospect broke out in his second minor league season in 2022. He hit 19 home runs with 69 RBI across 104 games at rookie ball, High-A, and Double-A.

Mayo then followed up that campaign by posting even better numbers in 2023. He slashed .290/.410/.563 at the plate with 29 home runs, 45 doubles, 99 RBI, and five stolen bases in 140 games at Double-A and Triple-A. Given his raw power, it was only a matter of time until the third baseman got his shot in the majors.

That became a reality during the 2024 season following a strong first few months for Mayo down in Triple-A. He eventually made his MLB debut on August 2, 2024. However, the 23-year-old really struggled in his first taste of the big leagues. He had just four hits across his first 41 at-bats (.098 batting average) to go with four runs scored, four walks, and 22 strikeouts across 17 games.

Therefore, it wasn't a surprise to see Mayo begin the 2025 season at Triple-A Norfolk. He looked overmatched at the plate in his first few major league plate appearances last year and needed to work on some things in the minors. However, MLB Pipeline's No. 11 overall prospect didn't have to wait too long to get his shot in the majors again.

Coby Mayo gets the call!

Mayo has been effective in AAA this season as he has flashed his elite power. The contact rates are solid and should hopefully lead to a more fruitful stint in MLB this time around.

Congratulations! pic.twitter.com/XY1N1K0azp

— Thomas Nestico (@TJStats) May 3, 2025

The Orioles promoted him to their major league roster a few days ago, and he should see plenty of playing time with Jordan Westburg (hamstring) on the 10-day injured list. Nevertheless, Mayo should only be added in deeper leagues right now.

He is 0-for-6 with two strikeouts in his second stint in the majors and hasn't looked great offensively in his major league career. Although it is too early to judge him after just six at-bats, there are better prospects to stash at this point in the season.

Hyeseong Kim, 2B/SS, Los Angeles Dodgers

Current Level: Los Angeles Dodgers
Availability: 19% rostered
2024 KBO stats: 127 G, .326/.383/.458, 11 HRs, 75 RBI, 90 R, 30 SB
2025 AAA stats: 28 G, .252/.328/.470, 5 HRs, 19 RBI, 22 R, 13 SB

When Los Angeles Dodgers utility specialist Tommy Edman (knee) landed on the 10-day IL, it paved the way for Kim to be called up by the team. The 26-year-old rookie signed with the Dodgers this past offseason after playing eight seasons in the Korea Baseball Organization (KBO). There, he had a career .304 batting average, 37 home runs, 150 doubles, 39 triples, and 211 stolen bases in 953 games.

Kim's best season in the KBO came last year when he hit .326 with 11 home runs, 26 doubles, four triples, 75 RBI, and 30 stolen bases in 127 games for the Kiwoom Heroes. Those 11 home runs and 75 RBI were both career highs for him.

We also saw a little bit of that power from Kim in his first 28 games at Triple-A Oklahoma City this season. He hit five home runs in 115 at-bats to go with 19 RBI, 22 runs scored, and 13 stolen bases. However, fantasy managers shouldn't really expect that power to carry over into the majors. The 26-year-old hit double-digit home runs just once in his KBO career (2024).

Kim, though, will be a weapon for the Dodgers on the base paths. He stole at least 25 bases in six of his eight years in the KBO, which included a career-high 46 stolen bases during the 2021 season. So, if you are in need of some stolen bases in your rotisserie leagues, the rookie could be a sneaky add in some 12-plus leagues.

Hyeseong Kim is racking up MLB firsts for the @Dodgers while swiping his second big league base:
2 hits
RBI
R pic.twitter.com/uNxYZjR3h4

— MLB Pipeline (@MLBPipeline) May 6, 2025

Kim started his first major league game on Monday and went 2-for-4 with one RBI and one stolen base against the Miami Marlins. He also came on as a pinch-runner in the ninth inning of Sunday's game and stole his first major league bag. There's no doubt the Dodgers will use his speed, making him someone to consider adding for stolen bases.

Gunnar Hoglund, SP, Athletics

Level: Athletics
Availability: 27% rostered
2024 AAA stats: 24 G (23 GS), 3.44 ERA, 119 K, 1.07 WHIP, 130 2/3 IP 
2025 AAA stats: 6 GS, 2.43 ERA, 30 K, 1.04 WHIP, 29 2/3 IP

It has been a long time coming for Hoglund to make his major league debut. He was selected by the Toronto Blue Jays in the first round of the 2021 MLB Draft before being dealt to the Athletics in the Matt Chapman trade a few months later. Although the right-hander only pitched eight innings in 2022 and struggled mightily in 2023, he really broke out last season.

Hoglund finished with a 3.44 ERA, a 1.07 WHIP, and 119 strikeouts in 24 games (23 starts) at Double-A and Triple-A in 2024. He also held opposing hitters to a .216 batting average while walking just 37 batters across 130 2/3 innings pitched.

Following that breakout campaign, Hoglund got off to a fantastic start at Triple-A Las Vegas this season. The 25-year-old allowed just eight runs across 29 2/3 innings (2.43 ERA) to go with 30 strikeouts and a 1.04 WHIP across his six starts. His best outing came back on April 27 when he threw five shutout innings with five strikeouts against Triple-A Round Rock.

That impressive showing earned Hoglund a promotion to the major league roster. He then made his MLB debut last week against the Miami Marlins. In that outing, the right-hander allowed just one run on six hits with seven strikeouts across six dominant innings. He didn't issue one walk and had a 30.6 percent whiff rate in that contest.

A's prospect Gunnar Hoglund in his first MLB start:

6 IP, 6 H, 1 ER, 0 BB, 7 K 👏 pic.twitter.com/fFlZKMNHaC

— B/R Walk-Off (@BRWalkoff) May 3, 2025

As a result, Hoglund could be a solid add in Week 6. He'll have a tougher matchup in his second career start against a solid Mariners offense. Seattle currently ranks fifth in runs per game this season. Still, the Athletics' No. 14 prospect is worth rolling with, considering the Mariners rank 20th in strikeouts per game (8.47).

If Hoglund pitches well again on Wednesday, there's a good chance that he stays in this rotation for the foreseeable future. The right-hander replaced J.T. Ginn (elbow) when he went on the 15-day IL, but the Athletics likely won't send him down if he continues to deliver on the mound. So, he's worth adding in some 12-plus team leagues.

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