Fantasy Baseball Prospect Risers - Rookies to Stash and Top Performers for Week 18

July 26, 2026

Jeremy's top fantasy baseball prospect risers, breakouts with big upside for Week 18 of 2026. He analyzes top MLB rookies and call-ups to stash who are surging.

Welcome to the Week 18 edition of the top prospect performers. In this weekly piece, we take a look at some of the top-performing minor leaguers who could matter in fantasy down the road. While some may be promoted more quickly than others, it's important to stay up to date on recent prospect performances so you're ready to add them when they do get the call.

The most notable recent prospect promotion was Tommy White, who was featured in an earlier edition of this piece. While he's not a priority add in shallow leagues, he should be on your fantasy radar for deeper leagues, and has so far enjoyed an 8-for-23 start to his career with two extra-base hits. There should be plenty more promotions as we progress through the second half of the year, and that's especially true once we near the expanded roster size in September.

This week, we'll take a look at one Triple-A pitcher who's making a case for a 2026 debut, along with two players in lower levels who are skyrocketing up dynasty rankings. Adding the right prospect at the right time could propel your team to a fantasy championship, as they oftentimes come with upside that is rare to find on the waiver wire. Without further ado, let's get into it.

Quinn Mathews, SP, St. Louis Cardinals

Cardinals No. 7, Overall N/A

You might remember Quinn Mathews as one of the quickest rising prospects of 2024, when he ascended from Low-A to Triple-A in his first year of professional baseball while posting a 2.76 ERA and 0.98 WHIP with 202 strikeouts and 49 walks in 143 ⅓ innings. He looked destined to reach the major leagues soon and make a big impact, before an injury-plagued season in 2025 completely tanked his value.

He missed time with a shoulder injury that held him out in early 2025, but what was more concerning was his performance after returning. The lefty saw a decrease in fastball velocity that fueled his breakout 2024 and struggled with mechanics, ultimately posting a 3.93 ERA and 1.55 WHIP. Not only did his strikeouts drop to 115 in 99 innings, but his control was nonexistent, with a whopping 16.8% walk rate that resulted in 74 free passes.

It's no surprise that Mathews entered 2026 as an afterthought for fantasy after the disastrous 2025, but he has done well to regain some of that form that made him a breakout star two seasons ago. He most recently displayed that upside in his last start on Friday, tossing seven shutout innings with 10 strikeouts against the Durham Bulls.

This wasn't just one good outing, either, as it marked his fourth straight quality start. In that span, the 25-year-old has posted a 1.04 ERA and 0.77 WHIP with 28 strikeouts and six walks in 26 innings. For the season as a whole, his ERA now sits at 3.13, and his WHIP is 1.14. While it's not at the same level as his 35.4% strikeout rate in 2024, the youngster has punched batters out at a clip of 29.8% this season, which is a noticeable increase compared to last season.

Quinn Mathews recorded his first double-digit strikeout game since 2024 tonight.

Over his last nine starts, he's posted a 1.55 ERA with a 30.9% K% and 9.9% BB%. pic.twitter.com/dQCfLQmQmq

— Kareem Haq (@KareemSSN) July 25, 2026

The biggest thing he will need to keep in check is his walks, as his walk rate is still too high at 14.0%. However, that rate is inflated by poor play early on, as Mathews walked 16 batters in his first four starts of the year. He's gotten it more under control as of late during this recent hot stretch, but it's something to watch moving forward.

The Cardinals are far from having a dominant major league rotation, so it may not be long before they give the youngster a shot. Matthew Liberatore currently has a 5.18 ERA and 1.52 WHIP on the season, and St. Louis might be motivated to make a change if no improvements are being made.

Verdict: Monitor for promotion

Theo Gillen, OF, Tampa Bay Rays

Rays No. 1, Overall No. 9

Theo Gillen was a solid prospect last season, slashing .267/.433/.387 with five home runs and 36 stolen bases in 73 games at Low-A, but the one thing that he was clearly missing was power. There were hopes that he would grow into more power, and there were clear signs of it from the start this season, which is why I featured him in an early edition of this piece.

In that piece, I said that he could become one of the most highly-touted prospects in fantasy if he maintained that power, and now is a good time to check back in on Gillen and confirm that that's the case. He went 2-for-3 on Friday with his fourth home run in the past seven games, bringing his season total to 16 to go along with a .321/.427/.563 slash line.

"Remember the name Theo Gillen!"@RaysBaseball's No. 1 prospect rips a walk-off homer to cap a multihit, three-RBI performance for Double-A @BiscuitBaseball: pic.twitter.com/sh4VVm5LcD

— MLB Pipeline (@MLBPipeline) July 25, 2026

What's even more impressive is that the 20-year-old is now doing this at Double-A, where he has spent the past 21 games with a 20.8% strikeout rate, which is actually a three percent improvement over his rate at High-A. It's all coming together for the youngster, whose speed is still as apparent as ever, with 36 steals in 78 games on the year.

Gillen is shaping up to be a true five-category contributor with fantasy upside that is off the charts. There's no need to worry about him in redraft leagues for 2026, as he's still a 20-year-old getting his first taste of Double-A, but expect him to be one of the most talked about minor leaguers heading into 2027.

Verdict: Elite dynasty asset

Kendry Chourio, SP, Kansas City Royals

Royals No. 1, Overall No. 66

Kendry Chourio is another prospect who will not matter for fantasy this season, but is a name you need to know moving forward. He was signed by the Royals as an international free agent in 2025 at just 16 years old, and has been impressive in 2026, to say the least.

On July 19th, the youngster delivered five no-hit innings while striking out 10 in his fifth start at High-A. That start is noteworthy enough in its own right, but it's even more impressive to come from a player who is still only 18 years old in a league that is usually far too advanced for someone his age. He followed that up with another solid start on Saturday, allowing one run in six strong innings.

MLB's No. 9 RHP prospect Kendry Chourio (@Royals) retires the first 13 batters he faces in a stingy outing for the High-A @QCRiverBandits:
5 IP
0 H 👀
0 R
2 BB
10 K (T-career high)
18 swings-and-misses pic.twitter.com/mzdq3pJU99

— MLB Pipeline (@MLBPipeline) July 19, 2026

On the season, the righty has posted a 2.06 ERA and 0.85 WHIP with 79 strikeouts and 14 walks in 78 ⅔ innings. He's exhibited a 4.5% walk rate that shows pristine control, which is, once again, a trait that is rare to find in such a young pitcher. While the strikeout numbers don't necessarily blow you away, his stuff has plenty of potential for that to increase down the line.

Chourio's fastball has reached over 98 mph this season and sits in the mid-90s, while he also throws a curveball, changeup, and slider that all have room to grow into a very effective and complete arsenal. He has two double-digit strikeout efforts on the year, so he may already be starting to put all the pieces together.

It's risky to become too attached to pitching prospects in dynasty leagues, especially ones this young, as so much can change if they're unfortunate enough to suffer a major arm injury. However, Chourio is less volatile than the average young pitcher due to his elite control and his experience in advanced competition, so expect him to rise up the dynasty rankings quickly.

Verdict: Fast-rising dynasty asset

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