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Andy looks at five sneaky fantasy baseball waiver wire pickups for starting pitchers in Week 10 (2025) on hot streaks, and sees if they can sustain their success.
With another week of MLB action in the books, it is time to take a deep dive into some under-the-radar pitchers who have begun to enjoy some success. While these pitchers are not viewed as bona fide "must-start" options, they could gradually enter that group by the end of the season.
In this piece, we will take a look at a pitcher in San Francisco who has transitioned well to a starting role. In addition, we will analyze a pitcher from Houston who has flashed high strikeout upside after his nearly two-year absence.
Who should fantasy managers be targeting this week? Let's dive in!
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Hayden Birdsong, San Francisco Giants
35% Rostered
San Francisco Giants right-hander Hayden Birdsong opened the season in the bullpen but was recently shifted to the starting rotation following Jordan Hicks' disappointing start to the season.
During his 23 1/3 innings of relief, Birdsong was effective, posting a 2.31 ERA with a 1.29 WHIP. He struck out 25 batters but often struggled with his command, posting a modest 3.9 BB/9.
Last summer, Birdsong was deployed out of the rotation and showed similar command issues. Across 72 frames last summer, Birdsong posted a hefty 12.7% walk rate, which placed him in the first percentile among qualified pitchers. However, he did show solid upside at times, as he struck out 88 batters.
Since returning to the rotation, Birdsong has taken a significant step forward in his development. Through three starts, the former sixth-round pick has logged 14 2/3 innings of five-run ball (four earned runs). He has yet to allow a home run and has struck out 15 batters. More importantly, Birdsong has shown elite command.
During this stretch, he has served up just two total walks.
Since transitioning to a starter, Birdsong has opted to rely less on his changeup. In April, he deployed his changeup 26.0% of the time (second-most used pitch). However, in May and at his first start in June, Birdsong relied on this pitch just 15.4% and 15.9% of the time, respectively. Instead, he has begun to increase his curveball and slider usage.
In April, he threw his slider 22.6% of the time and his curveball 6.8% of the time. However, in May, he bumped this usage up to 32.0% and 16.6%, respectively. He showed similar usage in his start on June 1 against the Marlins, tossing his slider 28.4% of the time and his curveball 15.9% of the time, good for his second and third-most-used pitches.
In May, his slider became his primary whiff pitch, boasting a 34.0% whiff rate. In his most recent outing, his curveball did most of the damage, generating a high 40.0% whiff rate.
With improving control and a slider and curveball showing decent strikeout potential, Birdsong is worth adding in all standard leagues. If these pitches can continue to get him out of tough counts and keep his walk rate down, he could be poised to enjoy a breakout season.
It would be malpractice to send Hayden Birdsong back to the bullpen pic.twitter.com/Lfo7h0SMju
— Pitch Profiler (@pitchprofiler) June 1, 2025
Jack Leiter, Texas Rangers
33% Rostered
Jack Leiter had high expectations when he made his MLB debut last season. The Rangers drafted the Vanderbilt standout with the second overall pick in the 2021 MLB Draft. However, during his first 35 2/3 innings in the majors, Leiter struggled as he posted an 8.83 ERA with a 1.71 WHIP.
However, this season, the right-hander has begun progressing to the next level. During his first two starts, he looked like a potential breakout as he logged 10 innings of one-run ball with 10 strikeouts. However, he then dealt with a blister on his finger, which kept him in the 15-day IL through most of April.
He returned on April 27 and immediately took a step back, allowing two runs with four walks across two frames. Then, in his next two outings (9 1/3 innings), Leiter allowed 10 runs with 11 hits.
Despite the setback, the former top prospect has gotten himself back on track. Over his last four starts (23 2/3 innings), Leiter has held a strong 2.28 ERA with a 1.10 WHIP. Over this stretch, he has shown modest control with an 18:12 K:BB but has been able to limit the damage.
Is Leiter getting lucky, or is the breakout legit? Currently, he sits in the 20th percentile in xERA and 23rd percentile in barrel rate. This will surely catch up to him, given his high 11.9% walk rate. His two most-used pitches, his fastball and slider, are also due for significant regression. His fastball carries a .185 SLG, nearly 200 points lower than its .362 xSLG.
His sldier does not fare much better, holding a .274 wOBA, compared to the high .328 xwOBA it has under the hood.
Leiter could find value in favorable matchups, but should not be trusted as a must-start option for the time being.
Charlie Morton, Baltimore Orioles
20% Rostered
After posting a 9.45 ERA with a 2.17 WHIP across his first seven outings (26 2/3 innings), almost the entire fantasy baseball community wrote the 41-year-old off. However, Morton has enjoyed a strong May and continued his resurgence during his most recent outing on June 1.
Since the start of May, Morton has held a 3.00 ERA with a 1.00 WHIP across 27 innings, split between the rotation and long relief. During this stretch, he struck out 26 batters but showed strong command, allowing just six walks.
The catalyst for his sudden improvement is his curveball, which has been his primary pitch this season. In April, this pitch was among the worst in the majors, generating a hefty .532 xSLG with a .397 xwOBA. However, in May, this pitch generated a .373 xSLG with a .281 xwOBA and a similar .332 xSLG and .262 xWOBA during his first start in June.
This pitch has also shown steady improvement in the swing-and-miss department throughout the young season.
However, in May, his sinker overperformed, posting a near-perfect .100 SLG, which is significantly lower than the .349 xSLG under the hood.
While Morton should continue to find value as a deep-league streaming option, he lacks a full arsenal, which makes him risky in most standard leagues. Overall, Statcast places him in the second, third, and fifth percentiles in pitching run value, fastball run value, and breaking run value, which are not positive indicators.
Morton can be trusted in deeper formats, but fantasy managers should expect some regression throughout June.
Lance McCullers Jr., Houston Astros
15% Rostered
After not pitching since the 2022 MLB campaign, recovering from Tommy John and numerous setbacks along the way, Lance McCullers Jr. made his long-awaited return to the bump on May 4. In this outing, the right-hander held his own, tossing 3 2/3 shutout innings with a 4:3 K:BB.
However, his next outing would cause several optimistic fantasy managers to cut ties. He allowed three hits and seven runs in just 1/3 of an inning to the Cincinnati Reds.
Despite the blowup start, McCullers bounced back and has been able to return to form. Over his last three outings, he has held a 3.14 ERA with a 1.33 WHIP. During this stretch, the right-hander has struck out 22 batters (in 14 1/3 innings) and allowed just two walks. Much of his strikeout production came from his last two outings, where he struck out 20 batters in just 10 1/3 innings.
All 12 of Lance McCullers Jr.'s strikeouts: pic.twitter.com/cioeIsHg80
— Ari Alexander (@AriA1exander) May 28, 2025
Is McCullers back?
His primary pitch, his slider, is due for some significant positive regression. Through his first month of action, it has generated a strong .202 xBA, much lower than the .304 BA it holds. It also carries a 28.0% whiff rate, nearly identical to the 31.8% whiff rate this pitch held in 2022.
The bad news is that McCullers does not have a fastball. His second-most-used pitch, his changeup, is solid, boasting a .302 xwOBA, but his sinker (third most-used) has been his Achilles heel. This pitch has generated a high .353 xBA (.414 BA) with a .593 xSLG (.706 SLG). He occasionally mixes in his No. 4 pitch, his curveball, which has been an elite whiff pitch (58.6% whiff rate).
While his strikeout numbers should remain strong with his slider, changeup, and stellar curveball, his ratios could be hard to trust due to his sinker. He currently sits in the 26th percentile in xERA and 31st percentile in barrel rate. Do not be afraid to add McCullers off your waiver wire if you're falling behind in strikeouts.
However, be cautious when deploying him. A tough matchup can set your ratios back significantly.
Adrian Houser, Chicago White Sox
15% Rostered
The final pitcher we will examine is Adrian Houser of the Chicago White Sox. After posting a 5.84 ERA and a 1.53 WHIP across 69 1/3 innings in 2024, Houser looked like an entirely new pitcher in 2025, logging 18 1/3 innings with a 1.47 ERA and a 0.98 WHIP.
Houser had a late start to the MLB season as he was released by the Rangers after spending time with their Triple-A affiliate, the Round Rock Express. The White Sox signed Houser on May 20, and he made his season debut on the same day. During his first two outings, he tossed back-to-back six-inning shutouts with eight total punchouts.
He took a slight step back in his most recent outing, allowing three runs and eight hits across 6 1/3 frames to the Orioles.
Last season, Houser leaned on his sinker quite heavily, deploying it 44.5% of the time. However, this season, the 32-year-old has lowered that usage to 37.3%, which has allowed him to mix in his four-seamer more frequently. These two pitches (combined 62.3% usage rate) have generated an impressive .297 xwOBA and a .284 xwOBA, respectively.
His whiffs come from his curveball, which has generated a strong 37.5% whiff rate with a .275 xwOBA, much-improved compared to the 15.0% whiff rate and .377 xwOBA it generated the previous season.
With a strong command of his pitches (7.1% walk rate) and the ability to limit hard contact evident in his stellar 3.9% barrel rate, Houser is an intriguing name to target in deeper formats. While fantasy managers should expect some regression given his career 4.13 ERA, Houser may be taking the proper steps to enjoy a productive 2025 campaign.
Welcome to Chicago, Adrian Houser
6.0 IP, 2 H, 0 R, 3 BB, 2 K
90 pitches - 56 strikes (8 swinging)
— Sox On 35th (@SoxOn35th) May 21, 2025
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