3 Impact Fantasy Baseball Prospects To Stash - Owen Caissie, Quinn Mathews, C.J. Kayfus

Three top fantasy baseball prospects - Owen Caissie, Quinn Mathews, C.J. Kayfus - that can make big impacts. These MLB prospects are waiver wire pickups or stashes.

Stashing the right prospect can provide a much-needed boost to your fantasy team. Last season, fantasy managers saw several top prospects make an impact once they reached the MLB level, such as James Wood and Junior Caminero.

In this piece, we will analyze three players who are currently performing at a high level at Triple-A and are knocking on the big-league door.

Should those players be left on the waiver wire, or should fantasy managers add them before their breakout? Let's dive in!

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Owen Caissie, OF, Chicago Cubs

Current Level: AAA
Availability: 5% rostered
2025 AAA stats: 63 G, .265/.368/.500, 18 2B, 11 HR, 3 SB

The Chicago Cubs outfield prospect has been one of the most productive hitters at Triple-A since the start of June and is making a strong case to join the MLB roster. Since June 1, Caissie has held a .354/.455/.6366 slash line with seven doubles, four home runs, 12 RBI, one stolen base, and a 121:10 K:BB (through 18 games).

Across 61 total games with Triple-A Iowa, Caissie has posted a .268/.372/.502 line with 17 doubles, two triples, and 11 home runs.

The former 45th overall pick spent the entire 2024 campaign with Triple-A Iowa and enjoyed a similar production, posting a slightly lower .278/.375/.472 line with 29 doubles and 19 round-trippers across 127 games.

Throughout his time in the Cubs' system, Caissie has typically spun an entire campaign at a level before earning a promotion at the start of the following season.

While he has been one of the most impressive hitters at Triple-A this season, does the Notre Dame Catholic SS product have a viable path to join Chicago in the second half?

Caissie has a near-impossible path without a significant injury occurring. Currently, the Cubs boast one of the best outfields in baseball, featuring gold-glover Ian Happ in left field, MVP candidate Pete Crow-Armstrong in center field, and superstar Kyle Tucker in right field.

What about DH? Well, former everyday right fielder Seiya Suzuki owns that role and is in no danger of losing any plate appearances.

As a result, Caissie will only get the call if one of those four suffers a significant injury. In addition, one injury may not even be enough, as fellow Triple-A teammate Moises Ballesteros could even make another call to the bigs before Caissie.

Even though he appears to be a budding star, Caissie will have to wait until 2026 to reach the majors.

Owen Caissie is absolutely destroying the baseball right now. Unfortunately there is just no room for him on the ML roster. Wonder how coveted he becomes at the deadline if he keeps this up

— David Kep (@Davey_Baseball) June 18, 2025

-Written by Andy Smith

Quinn Mathews, SP, St. Louis Cardinals

Current Level: AAA
Availability: 5% rostered
2025 AAA stats: 26 IP, 3.81 ERA, 1.73 WHIP, 27 SO, 24 BB

After missing most of the season with left shoulder inflammation, the top pitching prospect in St. Louis is back in action and once again knocking on the MLB door. In his most recent outing on June 18, Mathews allowed just one hit across five shutout frames against the Norfolk Tides. In this start, the left-hander struck out six batters and allowed two walks.

Through 26 Triple-A appearances this season, the left-hander has posted a solid 3.86 ERA and 1.73 WHIP. However, many of his ratios are inflated due to his rough start, which was likely due to his injury.

Over his last 13 innings (three starts), Mathews has allowed just two runs, six walks, seven hits, and has struck out 17 batters.

This is an excellent sign as the Stanford product struggled during his first taste of Triple-A last season, posting a hefty 6.48 ERA and a 1.93 WHIP across 16 2/3 innings of work. However, his time with Low-A, High-A, and Double-A was quite impressive, as Mathews posted a 2.27 ERA and a 0.85 WHIP through 126 2/3 innings of work.

While a debut may not be imminent, he should remain in play to make a second-half MLB debut.

LHP Quinn Mathews (AAA) was nearly unhittable this afternoon, tossing 5.0 scoreless innings while allowing one base hit (single) and punching out 6.

Since being activated for the IL on May 31, the southpaw is 2-0 with a 2.30 ERA in 4 starts. pic.twitter.com/nxsjO4QPC7

— Cardinals Player Development (@CardsPlayerDev) June 18, 2025

- Written by Andy Smith

C.J. Kayfus, 1B, Cleveland Guardians

Current Level: AAA
Availability: 5% rostered
2025 AAA stats: 44 G, .309/.380/.552, 11 2B, 7 HR, 2 SB

C.J. Kayfus has been a fast riser within the Cleveland system after being selected with the 93rd overall pick in the 2023 MLB Draft out of Miami. Kayfus began his professional career shortly after the draft with Low-A and held a solid .271/.429/.542 line across 17 games.

In 2024, Kayfus began his season with High-A Lake County and continued to swing a hot bat. Through 40 games, the first baseman posted a stellar .338/.437/.538 salash line with 12 doubles, two triples, and seven home runs. During this stretch, he held an impressive 33:23 K:BB. He then earned a taste of Double-A in the second half.

Through his first 67 games in the upper levels of the minor leagues, Kayfus took a slight step back, posting a .263/.366/.470 line with 14 doubles and 10 long balls.

He began the 2025 campaign with Double-A Akron as expected. As Kayfus showed in 2024, he immediately took a step forward at the start of the season. During his second taste of Double-A action, the No. 5-ranked prospect in the system posted an impressive .364/.475/.591 line with 14:11 K:BB through 18 games. This start earned him an early promotion to Triple-A.

With Triple-A, Kayfus has continued to swing a hot bat and is quickly approaching his MLB debut. In his first 43 games with Triple-A Columbus, Kayfus has posted a .315/.383/.562 line with 11 doubles, four triples, seven long balls, and a 50:18 K:BB.

Does this performance truly matter?

Under the hood, Kayfus holds stellar metrics that suggest he is more than ready to join Cleveland. In 2024, Kayfus posted a 24.3% K rate, which was lowered by one point in 2025, despite facing tougher competition. He has also increased his wOBA by over 20 points (.438 (2025) - .410 (2024)) and raised his wRC+ from 159 to 172.

Currently, Carlos Santana holds down first base in the majors and does not appear to be in any danger of losing playing time, despite his .248/.342/.376 line. However, at DH, Kyle Manzardo has cooled down following his hot start and could open the door for Kayfus. Since May 21 (last 20 games), Manzardo has held a .169/.229/.262 line.

He has even begun to lose time to David Fry at the DH spot.

If Kayfus continues to produce at Triple-A, he will force their hand.

The @CleGuardians' C.J. Kayfus, who is slashing .339/.430/.558 this season, enters the Top 100 Prospects list after Agustín Ramírez graduates: https://t.co/KSn9yLGUz6 pic.twitter.com/TcjMSIclJR

— MLB Pipeline (@MLBPipeline) June 1, 2025

- Written by Andy Smith

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