Fantasy Baseball League Winners: Unlikely Aces Worth A Roster Spot? (Week 19)

Joey Pollizze deep dives into four fantasy baseball starting pitchers to decide if their surprisingly good form merits a roster spot or staying on the waiver wire for Week 19 (2025).

Welcome, RotoBallers, to our weekly unlikely aces piece. Every week of the fantasy season, we identify whether emerging pitchers are for real or not. We will dive into their recent numbers and determine if these emerging pitchers are worth a roster spot. 

In this article, we will look at whether Michael Wacha, Jack Leiter, Lucas Giolito, and Will Warren are worth grabbing in Week 19 of the fantasy baseball season. These four pitchers continue to see their rostership climb in all formats. 

So, should fantasy managers pick up Wacha, Leiter, Giolito, and Warren in fantasy? Are these unlikely aces worth a roster spot in Week 19? Let's dive in and find out.

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Michael Wacha, Kansas City Royals

Wacha continues to be an underrated pitcher in both real life and in fantasy. Despite pitching well for most of the season, the right-hander is only rostered in 43% of Yahoo! leagues. That feels extremely low for a pitcher who currently owns a 3.38 ERA across 125 1/3 innings pitched. This consistency is also nothing new for him, as the veteran has finished with a sub-3.40 ERA in three straight seasons. 

What has been most impressive is how Wacha has looked on the mound over the last few weeks. He has a 1.48 ERA across his last four starts and hasn't allowed more than one run in any of those outings. In his most recent start, the 34-year-old tossed eight innings of one-run ball with five strikeouts against the first-place Toronto Blue Jays. 

Michael Wacha in Toronto:

8.0 IP
3 H
1 ER
0 BB
5 SO

His first 8-inning start since June 2022. pic.twitter.com/cw2o2VRby3

— StatMuse (@statmuse) August 2, 2025

It's hard not to love Wacha in fantasy for the rest of the season, considering how consistent he has been. He has allowed three runs or fewer in 16 of his 22 starts and has delivered nine quality starts in 2025. Those numbers have really made the one-time All-Star fly under the radar in most fantasy leagues this year. 

He continues to lean on his fastball the most at 29.4%, but Wacha does a nice job mixing up his pitches with a six-pitch arsenal. His best pitch has been his changeup, which comes as no surprise. Opposing hitters struggled against that pitch in 2024, and nothing has changed this year. The Royals pitcher has a 29.9% whiff rate on that changeup through 22 starts. 

Verdict: While Wacha might not be the biggest name, he deserves to be rostered in almost all 12-team leagues at this point. He isn't allowing much hard contact and is one of the few pitchers on the waiver wire with a sub-3.40 ERA. With a 33.1% hard-hit rate, a 6.8% walk rate, and a 7.3% barrel rate, the veteran is a sneaky pitcher add in Week 19. 

Jack Leiter, Texas Rangers

Like any young pitcher, Leiter has had plenty of struggles this season. He has allowed six earned runs in multiple outings and had a whopping 4.55 ERA across his first 13 starts. However, the Rangers pitcher has had much better results since giving up six earned runs in a start against the Royals on June 17. 

Leiter has allowed two runs or fewer in five of his past six starts, and his swing-and-miss stuff has been a big reason for his success during this span. The 25-year-old has struck out at least seven batters in four of those six outings, including a seven-punchout game against the Mariners in his last start on August 1. 

In that outing on August 1, Leiter's swing-and-miss stuff was on full display. He generated 19 whiffs, and we saw an uptick in his curveball usage. The right-hander usually throws that pitch only 9.5% of the time, but that number was up to 22% in Friday's start. The results: six whiffs on 20 curveballs thrown. 

The curveball hasn't been a consistent pitch for Leiter this season. Opposing hitters are batting an absurd .300 with a .600 slugging percentage, and that pitch only has a 9.5% putaway rate. However, if the Vanderbilt product can get more swing-and-miss on that curveball -- like he did against the Mariners -- he could emerge as a solid fantasy option. 

Verdict: It has been encouraging to see Leiter pitch much better over the past few weeks. He has completed six innings in two of his past three starts, and his strikeout numbers are trending up. However, let's give it one more start before we add him because there are a few concerns surrounding him at this point in the season. 

His walk rate (11.6%), barrel rate (10.9%), expected ERA (4.68), and hard-hit rate (43.8%) all rank in the 25th percentile or worse. So, he's only an add in 15-team leagues right now until we see how he navigates that Yankees offense on Wednesday night. 

Lucas Giolito, Boston Red Sox 

After missing the entire 2024 season due to an elbow injury, Giolito is having a resurgent season. He has a 3.57 ERA and 81 strikeouts across 95 2/3 innings pitched and is arguably coming off his best start of the year. The right-hander threw eight innings of one-run ball with four strikeouts against the Houston Astros on August 3. 

That outing marked the 10th time that Giolito has allowed one run or fewer in a start this season. Even though the 31-year-old is on pace to finish with his best numbers since 2021, the Red Sox pitcher is still available in over 40% of Yahoo! leagues. 

Lucas Giolito in 10 starts since June 10:

🔺7-1
🔺62 IP
🔺2.03 ERA
🔺0.95 WHIP
🔺23.4 K%

He’s lowered his ERA from 6.42 ➡️ 3.57. AL Comeback Player of the Year? pic.twitter.com/O74abebRDM

— Gordo (@BOSSportsGordo) August 4, 2025

There's no doubt that Giolito is having a bounce-back season, but not much has changed for him on the mound. His pitch mix has stayed relatively the same from the prior seasons, and his changeup remains a major weapon for him in his four-pitch arsenal. Opposing hitters are batting just .190 with 17 strikeouts against that pitch this season. 

Unfortunately, some regression is likely headed his way over the final months. His expected ERA (5.10) is 153 points higher than his actual ERA (3.57), and his whiff rate (22.9%), barrel rate (9.6%), and expected batting average against (.279) all rank in the bottom half of the league. 

Verdict: Considering Giolito has some poor metrics, it's only a matter of time until his overall numbers start to drop. Therefore, he isn't necessarily a must-add in Week 19. He should only be started in the right matchups moving forward, making him only a streaming option at best at this point in the year. 

Will Warren, New York Yankees

The potential has been there for Warren to be a solid fantasy option. He has had plenty of strong starts this season, and it's hard to ignore his swing-and-miss stuff. Some of his best outings this year included 5 2/3 shutout innings with 10 strikeouts against the Rangers on May 20 and six innings of three-run ball with a career-high 11 strikeouts against the Angels on June 17. 

"I don't think we're surprised, because his stuff really plays."

Aaron Boone was asked if he sees more double-digit strikeout games in Will Warren's future: pic.twitter.com/HH3ByJbhhG

— Yankees Videos (@snyyankees) May 21, 2025

Warren has also pitched well over the last few weeks. He has allowed just three earned runs across his last 16 2/3 innings. In his most recent outing on Tuesday, the right-hander threw five shutout innings with five strikeouts against the Rangers. 

Although Warren has pitched better in recent games, he has been a very inconsistent fantasy option for most of the year. He has allowed at least five earned runs in two of his last eight starts, and those types of outings are a large reason why he is rostered in just 39% of Yahoo! leagues. Fantasy managers just haven't been able to trust him between starts. 

However, the biggest positive for Warren throughout his first full MLB season has been his elite fastball. He is leaning on that pitch the most at 39.8%, and 56 of his 128 strikeouts have come on that four-seam fastball. Given that opposing hitters are batting just .204 with a .222 expected batting average, his fastball has been a solid putaway pitch for him. 

Verdict: Warren has surely shown some nice things on the mound in 2025. He has an impressive 26.2% strikeout rate to go with a solid 25.2% whiff rate. Nonetheless, his overall inconsistency on the mound doesn't make him an add in most 12-team leagues. The Yankees pitcher has walked at least three batters in four of his past five starts, and his hard-hit rate (44.1%) ranks in the 22nd percentile.  

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